Microporous zirconium silicate for the treatment of hyperkalemia

ABSTRACT

The present invention relates to novel microporous zirconium silicate compositions that are formulated to remove toxins, e.g. potassium ions, from the gastrointestinal tract at an elevated rate without causing undesirable side effects. The preferred formulations are designed avoid increase in pH of urine in patients and/or avoid potential entry of particles into the bloodstream of the patient. Also disclosed is a method for preparing high purity crystals of ZS-9 exhibiting an enhanced level of potassium exchange capacity. These compositions are particularly useful in the therapeutic treatment of hyperkalemia.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.61/716,956, filed Oct. 22, 2012, and U.S. Provisional Application No.61/800,182, filed Mar. 15, 2013, the disclosures of each of which arehereby incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to pharmaceutical compositions comprisingnovel microporous zirconium silicate (“ZS”) compositions that arespecifically formulated at particular dosages to remove select toxins,e.g., potassium ions or ammonium ions, from the gastrointestinal tractat an elevated rate without causing undesirable side effects. Thepreferred formulations are designed to remove and avoid potential entryof particles into the bloodstream and potential increase in pH of urinein patients. The formulation is also designed to release less sodiuminto the blood. These compositions are particularly useful in thetherapeutic treatment of hyperkalemia and kidney disease. Also disclosedare microporous ZS compositions having enhanced purity and potassiumexchange capacity (“KEC”). Methods of treating acute, sub-acute, andchronic hyperkalemia have also been investigated. Disclosed herein areparticularly advantageous dosing regimens for treating different formsof hyperkalemia using the microporous ZS compositions noted above.

2. Description of the Related Art

Acute hyperkalemia is a serious life threatening condition resultingfrom elevated serum potassium levels. Potassium is a ubiquitous ion,involved in numerous processes in the human body. It is the mostabundant intracellular cation and is critically important for numerousphysiological processes, including maintenance of cellular membranepotential, homeostasis of cell volume, and transmission of actionpotentials. Its main dietary sources are vegetables (tomatoes andpotatoes), fruit (oranges, bananas) and meat. The normal potassiumlevels in plasma are between 3.5-5.0 mmol/L with the kidney being themain regulator of potassium levels. The renal elimination of potassiumis passive (through the glomeruli) with active reabsorption in theproximal tubule and the ascending limb of the loop of Henle. There isactive excretion of potassium in the distal tubules and the collectingduct, both of these processes are controlled by aldosterone.

Increased extracellular potassium levels result in depolarization of themembrane potential of cells. This depolarization opens somevoltage-gated sodium channels, but not enough to generate an actionpotential. After a short period of time, the open sodium channelsinactivate and become refractory, increasing the threshold to generatean action potential. This leads to impairment of the neuromuscular-,cardiac- and gastrointestinal organ systems, and this impairment isresponsible for the symptoms seen with hyperkalemia. Of greatest concernis the effect on the cardiac system, where impairment of cardiacconduction can lead to fatal cardiac arrhythmias such as asystole orventricular fibrillation. Because of the potential for fatal cardiacarrhythmias, hyperkalemia represents an acute metabolic emergency thatmust be immediately corrected.

Hyperkalemia may develop when there is excessive production of serumpotassium (oral intake, tissue breakdown). Ineffective elimination,which is the most common cause of hyperkalemia, can be hormonal (as inaldosterone deficiency), pharmacologic (treatment with ACE-inhibitors orangiotensin-receptor blockers) or, more commonly, due to reduced kidneyfunction or advanced cardiac failure. The most common cause ofhyperkalemia is renal insufficiency, and there is a close correlationbetween degree of kidney failure and serum potassium (“S-K”) levels. Inaddition, a number of different commonly used drugs cause hyperkalemia,such as ACE-inhibitors, angiotensin receptor blockers, potassium-sparingdiuretics (e.g. amiloride), NSAIDs (such as ibuprofen, naproxen,celecoxib), heparin and certain cytotoxic and/or antibiotic drugs (suchas cyclosporin and trimethoprim). Finally, beta-receptor blockingagents, digoxin or succinylcholine are other well-known causes ofhyperkalemia. In addition, advanced degrees of congestive heart disease,massive injuries, burns or intravascular hemolysis cause hyperkalemia,as can metabolic acidosis, most often as part of diabetic ketoacidosis.

Symptoms of hyperkalemia are somewhat non-specific and generally includemalaise, palpitations and muscle weakness or signs of cardiacarrhythmias, such as palpitations, brady-tachycardia ordizziness/fainting. Often, however, the hyperkalemia is detected duringroutine screening blood tests for a medical disorder or after severecomplications have developed, such as cardiac arrhythmias or suddendeath. Diagnosis is obviously established by S-K measurements.

Treatment depends on the S-K levels. In milder cases (S-K between 5-6.5mmol/1), acute treatment with a potassium binding resin (Kayexalate®),combined with dietary advice (low potassium diet) and possiblymodification of drug treatment (if treated with drugs causinghyperkalemia) is the standard of care; if S-K is above 6.5 mmol/1 or ifarrhythmias are present, emergency lowering of potassium and closemonitoring in a hospital setting is mandated. The following treatmentsare typically used:

-   -   Kayexalate®, a resin that binds potassium in the intestine and        hence increases fecal excretion, thereby reducing S-K levels.        However, as Kayexalate® has been shown to cause intestinal        obstruction and potential rupture. Further, diarrhea needs to be        simultaneously induced with treatment. These factors have        reduced the palatability of treatment with Kayexalate®.    -   Insulin IV (+ glucose to prevent hypoglycemia), which shifts        potassium into the cells and away from the blood.    -   Calcium supplementation. Calcium does not lower S-K, but it        decreases myocardial excitability and hence stabilizes the        myocardium, reducing the risk for cardiac arrhythmias.    -   Bicarbonate. The bicarbonate ion will stimulate an exchange of        K+ for Na+, thus leading to stimulation of the sodium-potassium        ATPase.    -   Dialysis (in severe cases).

The only commercial pharmacologic modality that actually increaseselimination of potassium from the body is Kayexalate®; however, due tothe need to induce diarrhea, Kayexalate® cannot be administered on achronic basis, and even in the acute setting, with the accompanying needto induce diarrhea, combined with only marginal efficacy and a foulsmell and taste, reduces its usefulness.

The use of ZS or titanium silicate microporous ion exchangers to removetoxic cations and anions from blood or dialysate is described in U.S.Pat. Nos. 6,579,460, 6,099,737, and 6,332,985, each of which isincorporated herein in their entirety. Additional examples ofmicroporous ion exchangers are found in U.S. Pat. Nos. 6,814,871,5,891,417, and 5,888,472, each of which is incorporated herein in theirentirety.

The inventors have found that known ZS compositions may exhibitundesirable effects when utilized in vivo for the removal of potassiumin the treatment of hyperkalemia. Specifically, the administration of ZSmolecular sieve compositions has been associated with an incidence ofmixed leukocyte inflammation, minimal acute urinary bladder inflammationand the observation of unidentified crystals in the renal pelvis andurine in animal studies, as well as an increase in urine pH. Further,known ZS compositions have had issues with crystalline impurities andundesirably low cation exchange capacity.

The inventors disclosed novel ZS molecular sieves to address the problemassociated with existing hyperkalemia treatments, and novel methods oftreatment for hyperkalemia utilizing these novel compositions. See U.S.patent application Ser. No. 13/371,080 (U.S. Pat. Application Pub. No.2012-0213847 A1). In addition, the present inventors have disclosednovel processes for producing ZS absorbers with an improvedparticles-size distribution that can be prepared with methods avoidand/or reduce the need to screen ZS crystals. See U.S. ProvisionalApplication No. 61/658,117. Lastly, the present inventors have disclosednovel divalent cation (e.g., calcium and/or magnesium) loaded forms ofZS that are particularly beneficial for treating patients withhypocalcemia who are suffering from hyperkalemia. See U.S. ProvisionalApplication No. 61/670,415. The calcium loaded forms of ZS disclosed inthe '415 provisional may include magnesium in addition or as asubstitute for calcium. Each of these disclosures is incorporated hereinby reference in its entirety.

The inventors have discovered that delivery of ZS in the treatment ofhyperkalemia can be improved by the use of novel dosage forms.Specifically, the inventors have found that specific dosages of the ZS,when administered to a subject suffering from elevated levels ofpotassium, are capable of significantly decreasing the serum potassiumlevels in patients with hyperkalemia to normal levels. The inventorshave also found that these specific dosages are capable of sustainingthe lower potassium levels in patients for an extended period of time.

SUMMARY OF THE EMBODIMENTS OF THE INVENTION

Cation exchange compositions or products comprising ZS, when formulatedand administered at a particular pharmaceutical dose, are capable ofsignificantly reducing the serum potassium levels in patients exhibitingelevated potassium levels. In one embodiment, the patients exhibitingelevated potassium levels are patients with chronic or acute kidneydiseases. In another embodiment, the patients exhibiting elevatedpotassium levels have acute or chronic hyperkalemia.

In one embodiment, the dosage of the composition may range fromapproximately 1-20 grams of ZS, preferably 8-15 grams, more preferably10 grams. In another embodiment, the composition is administered at atotal dosage range of approximately 1-60 gram, preferably 24-45 grams,more preferably 30 grams.

In another embodiment, the composition comprises a molecular sieveshaving a microporous structure composed of ZrO₃ octahedral units and atleast one SiO₂ tetrahedral units and GeO₂ tetrahedral units. Thesemolecular sieves have the empirical formula:ApMxZr1-xSinGeyOmwhere A is an exchangeable cation selected from potassium ion, sodiumion, rubidium ion, cesium ion, calcium ion, magnesium ion, hydronium ionor mixtures thereof, M is at least one framework metal selected from thegroup consisting of hafnium (4+), tin (4+), niobium (5+), titanium (4+),cerium (4+), germanium (4+), praseodymium (4+), and terbium (4+), “p”has a value from about 1 to about 20, “x” has a value from 0 to lessthan 1, “n” has a value from about 0 to about 12, “y” has a value from 0to about 12, “m” has a value from about 3 to about 36 and 1≦n+y≦12. Thegermanium can substitute for the silicon, zirconium or combinationsthereof. Since the compositions are essentially insoluble in bodilyfluids (at neutral or basic pH), they can be orally ingested in order toremove toxins in the gastrointestinal system.

In an alternative embodiment, the molecular sieve is provided which hasan elevated cation exchange capacity, particularly potassium exchangecapacity. The elevated cation exchange capacity is achieved by aspecialized process and reactor configuration that lifts and morethoroughly suspends crystals throughout the reaction as described inU.S. patent application Ser. No. 13/371,080 (U.S. Pat. Application Pub.No. 2012-0213847 A1). In an embodiment of the invention, the improvedZS-9 crystal compositions (i.e., compositions where the predominantcrystalline form is ZS-9) had a potassium exchange capacity of greaterthan 2.5 meq/g, more preferably between 2.7 and 3.7 meq/g, morepreferably between 3.05 and 3.35 meq/g. ZS-9 crystals with a potassiumexchange capacity of 3.1 meq/g have been manufactured on a commercialscale and have achieved desirable clinical outcomes. It is expected thatZS-9 crystals with a potassium exchange capacity of 3.2 meq/g will alsoachieve desirable clinical outcomes and offer improved dosing forms. Thetargets of 3.1 and 3.2 meq/g may be achieved with a tolerance of ±15%,more preferably ±10%, and most preferably ±5%. Higher capacity forms ofZS-9 are desirable although are more difficult to produce on acommercial scale. Such higher capacity forms of ZS-9 have elevatedexchange capacities of greater than 3.5 meq/g, more preferably greaterthan 4.0 meq/g, more preferably between 4.3 and 4.8 meq/g, even morepreferably between 4.4 and 4.7 meq/g, and most preferably approximately4.5 meq/g. ZS-9 crystals having a potassium exchange capacity in therange of between 3.7 and 3.9 meq/g were produced in accordance withExample 14 below.

In one embodiment, the composition exhibits median particle size ofgreater than 3 microns and less than 7% of the particles in thecomposition have a diameter less than 3 microns. Preferably, less than5% of the particles in the composition have a diameter less than 3microns, more preferably less than 4% of the particles in thecomposition have a diameter less than 3 microns, more preferably lessthan 3% of the particles in the composition have a diameter of less than3 microns, more preferably less than 2% of the particles in thecomposition have a diameter of less than 3 microns, more preferably lessthan 1% of the particles in the composition have a diameter of less than3 microns, more preferably less than 0.5% of the particles in thecomposition have a diameter of less than 3 microns. Most preferably,none of the particles or only trace amounts have a diameter of less than3 microns.

The median and average particle size is preferably greater than 3microns and particles reaching a sizes on the order of 1,000 microns arepossible for certain applications. Preferably, the median particle sizeranges from 5 to 1000 microns, more preferably 10 to 600 microns, morepreferably from 15 to 200 microns, and most preferably from 20 to 100microns.

In one embodiment, the composition exhibiting the median particle sizeand fraction of particles in the composition having a diameter less than3 micron described above also exhibits a sodium content of below 12% byweight. Preferably, the sodium contents is below 9% by weight, morepreferably the sodium content is below 6% by weight, more preferably thesodium content is below 3% by weight, more preferably the sodium contentis in a range of between 0.05 to 3% by weight, and most preferably 0.01%or less by weight or as low as possible.

In one embodiment, the invention involves an individual pharmaceuticaldosage comprising the composition in capsule, tablet, or powdered form.In another embodiment of the invention, the pharmaceutical product ispackaged in a kit in individual unit dosages sufficient to maintain alowered serum potassium level. The dosage may range from approximately1-60 grams per day or any whole number or integer interval therein. Suchdosages can be individual capsules, tablets, or packaged powdered formof 1.25-20 grams of the ZS, preferably 2.5-15 grams of ZS, morepreferably 5-10 grams of ZS. In another embodiment, the ZS may be asingle unit dose of approximately 1.25-45 gram capsule, tablet orpowdered package. In another embodiment, the product may be consumedonce a day, three times daily, every other day, or weekly.

The compositions of the present invention may be used in the treatmentof kidney disease (e.g., chronic or acute) or symptoms of kidneydiseases, such as hyperkalemia (e.g., chronic or acute) comprisingadministering the composition to a patient in need thereof. Theadministered dose may range from approximately 1.25-20 grams of ZS,preferably 2.5-15 grams, more preferably 10 grams. In anotherembodiment, the total administered dose of the composition may rangefrom approximately 1-60 gram (14-900 mg/Kg/day), preferably 24-36 grams(350-520 mg/Kg/day), more preferably 30 grams (400 mg/Kg/day).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a polyhedral drawing showing the structure of microporous ZSNa2.19ZrSi3.01O9.11.•.2.71H2O (MW 420.71)

FIG. 2 shows particle size distribution of ZS-9 lot 5332-04310-A inaccordance with Example 8.

FIG. 3 shows particle size distribution of ZS-9 lot 5332-15410-A inaccordance with Example 8.

FIG. 4 shows particle size distribution of ZS-9 preclinical lot inaccordance with Example 8.

FIG. 5 shows particle size distribution of lot 5332-04310A w/o screeningin accordance with Example 9.

FIG. 6 shows particle size distribution of lot 5332-04310A 635 mesh inaccordance with Example 9.

FIG. 7 shows particle size distribution of lot 5332-04310A 450 mesh inaccordance with Example 9.

FIG. 8 shows particle size distribution of lot 5332-04310A 325 mesh inaccordance with Example 9.

FIG. 9 shows particle size distribution of lot 5332-04310A 230 mesh inaccordance with Example 9.

FIG. 10: XRD plot for ZS-9 prepared in accordance with Example 12.

FIG. 11: FTIR plot for ZS-9 prepared in accordance with Example 12.

FIG. 12: XRD plot for ZS-9 prepared in accordance with Example 14.

FIG. 13: FTIR plot for ZS-9 prepared in accordance with Example 14.

FIG. 14: Example of the Blank Solution Chromatogram

FIG. 15: Example of the Assay Standard Solution Chromatogram.

FIG. 16: Exemplary Sample Chromatogram.

FIG. 17: Reaction vessel with standard agitator arrangement.

FIG. 18: Reaction vessel with baffles for production of enhanced ZS-9

FIG. 19: Detail of baffle design for 200-L reaction vessel forproduction of enhanced ZS-9

FIG. 20: Treatment Period of ZS-9 in comparison to placebo over 48 hoursafter ingestion.

FIG. 21: Comparison of time of serum K decrease.

FIG. 22: Comparison of serum K increase following treatment.

FIG. 23: Rate of K excretion in urine.

FIG. 24: Daily urinary sodium excretion.

FIG. 25: XRD plot for H-ZS-9 prepared according to Example 20 batch5602-26812

FIG. 26: XRD plot for H-ZS-9 prepared according to Example 20 batch5602-28312

FIG. 27: XRD plot for H-ZS-9 prepared according to Example 20 batch5602-29112

FIG. 28: XRD plot for H-ZS-9 prepared according to Example 20 batch5602-29812

FIG. 29: XRD data for ZS crystals produced according to Example 20.

FIG. 30: XRD data showing ZS-8 impurities.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

The inventors have discovered novel ZS molecular sieve absorbers thataddress problems of adverse effects in the therapeutic use of molecularsieve absorbers, e.g., for the treatment of hyperkalemia. ZS has amicroporous framework structure composed of ZrO₂ octahedral units andSiO₂ tetrahedral units. FIG. 1 is a polyhedral drawing showing thestructure of microporous ZS Na2.19ZrSi3.01O9.11.•.2.71H2O (MW 420.71)The dark polygons depict the octahedral zirconium oxide units while thelight polygons depict the tetrahedral silicon dioxide units. Cations arenot depicted in FIG. 1.

The microporous exchanger of the invention has a large capacity andstrong affinity, i.e., selectivity, for potassium or ammonium. Eleventypes of ZS are available, ZS-1 through ZS-11, each having variousaffinities to ions have been developed. See e.g., U.S. Pat. No.5,891,417. UZSi-9 (otherwise known as ZS-9) is a particularly effectiveZS absorber for absorbing potassium and ammonium. These ZS have theempirical formula:A_(p)M_(x)Zr_(1-x)Si_(n)Ge_(y)O_(m)  (I)

where A is an exchangeable cation selected from potassium ion, sodiumion, rubidium ion, cesium ion, calcium ion, magnesium ion, hydronium ionor mixtures thereof, M is at least one framework metal selected from thegroup consisting of hafnium (4+), tin (4+), niobium (5+), titanium (4+),cerium (4+), germanium (4+), praseodymium (4+), and terbium (4+), “p”has a value from about 1 to about 20, “x” has a value from 0 to lessthan 1, “n” has a value from about 0 to about 12, “y” has a value from 0to about 12, “m” has a value from about 3 to about 36 and 1≦n+y≦12. Thegermanium can substitute for the silicon, zirconium or combinationsthereof. It is preferred that x and y are zero or both approaching zero,as germanium and other metals are often present in trace quantities.Since the compositions are essentially insoluble in bodily fluids (atneutral or basic pH), they can be orally ingested in order to removetoxins in the gastrointestinal system. The inventors of the presentinvention have noted that ZS-8 has an increased solubility as comparedto other forms of ZS (i.e., ZS-1-ZS-7, and ZSi-9-ZS-11). The presence ofsoluble forms of ZS including ZS-8 are undesirable since soluble formsof ZS may contribute to elevated levels of zirconium and/or silicates inthe urine. Amorphous forms of ZS may also be substantially soluble.Therefore, it is desirable to reduce the proportion of amorphousmaterial to the extent practicable.

The zirconium metallates are prepared by a hydrothermal crystallizationof a reaction mixture prepared by combining a reactive source ofzirconium, silicon and/or germanium, optionally one or more M metal, atleast one alkali metal and water. The alkali metal acts as a templatingagent. Any zirconium compound, which can be hydrolyzed to zirconiumoxide or zirconium hydroxide, can be used. Specific examples of thesecompounds include zirconium alkoxide, e.g., zirconium n-propoxide,zirconium hydroxide, zirconium acetate, zirconium oxychloride, zirconiumchloride, zirconium phosphate and zirconium oxynitrate. The sources ofsilica include colloidal silica, fumed silica and sodium silicate. Thesources of germanium include germanium oxide, germanium alkoxides andgermanium tetrachloride. Alkali sources include potassium hydroxide,sodium hydroxide, rubidium hydroxide, cesium hydroxide, sodiumcarbonate, potassium carbonate, rubidium carbonate, cesium carbonate,sodium halide, potassium halide, rubidium halide, cesium halide, sodiumethylenediamine tetraacetic acid (EDTA), potassium EDTA, rubidium EDTA,and cesium EDTA. The M metals sources include the M metal oxides,alkoxides, halide salts, acetate salts, nitrate salts and sulfate salts.Specific examples of the M metal sources include, but are not limited totitanium alkoxides, titanium tetrachloride, titanium trichloride,titanium dioxide, tin tetrachloride, tin isopropoxide, niobiumisopropoxide, hydrous niobium oxide, hafnium isopropoxide, hafniumchloride, hafnium oxychloride, cerium chloride, cerium oxide and ceriumsulfate.

Generally, the hydrothermal process used to prepare the zirconiummetallate or titanium metallate ion exchange compositions of thisinvention involves forming a reaction mixture which in terms of molarratios of the oxides is expressed by the formulae:aA₂O:bMO_(q/2):1-bZrO₂ :cSiO₂ :dGeO₂ :eH₂Owhere “a” has a value from about 0.25 to about 40, “b” has a value fromabout 0 to about 1, “q” is the valence of M, “c” has a value from about0.5 to about 30, “d” has a value from about 0 to about 30 and “e” has avalue of 10 to about 3000. The reaction mixture is prepared by mixingthe desired sources of zirconium, silicon and optionally germanium,alkali metal and optional M metal in any order to give the desiredmixture. It is also necessary that the mixture have a basic pH andpreferably a pH of at least 8. The basicity of the mixture is controlledby adding excess alkali hydroxide and/or basic compounds of the otherconstituents of the mixture. Having formed the reaction mixture, it isnext reacted at a temperature of about 100° C. to about 250° C. for aperiod of about 1 to about 30 days in a sealed reaction vessel underautogenous pressure. After the allotted time, the mixture is filtered toisolate the solid product which is washed with deionized water, acid ordilute acid and dried. Numerous drying techniques can be utilizedincluding vacuum drying, tray drying, fluidized bed drying. For example,the filtered material may be oven dried in air under vacuum.

To allow for ready reference, the different structure types of the ZSmolecular sieves and zirconium germanate molecular sieves have beengiven arbitrary designations of ZS-1 where the “1” represents aframework of structure type “1”. That is, one or more ZS and/orzirconium germanate molecular sieves with different empirical formulascan have the same structure type.

The X-ray patterns presented in the following examples were obtainedusing standard X-ray powder diffraction techniques and reported in U.S.Pat. No. 5,891,417. The radiation source was a high-intensity X-ray tubeoperated at 45 Kv and 35 ma. The diffraction pattern from the copperK-alpha radiation was obtained by appropriate computer based techniques.Flat compressed powder samples were continuously scanned at 2° (20) perminute. Interplanar spacings (d) in Angstrom units were obtained fromthe position of the diffraction peaks expressed as 2θ where θ is theBragg angle as observed from digitized data. Intensities were determinedfrom the integrated area of diffraction peaks after subtractingbackground, “I_(o)” being the intensity of the strongest line or peak,and “I” being the intensity of each of the other peaks.

As will be understood by those skilled in the art, the determination ofthe parameter 20 is subject to both human and mechanical error, which incombination can impose an uncertainty of about ±0.4 on each reportedvalue of 20. This uncertainty is, of course, also manifested in thereported values of the d-spacings, which are calculated from the 0values. This imprecision is general throughout the art and is notsufficient to preclude the differentiation of the present crystallinematerials from each other and from the compositions of the prior art. Insome of the X-ray patterns reported, the relative intensities of thed-spacings are indicated by the notations vs, s, m and w which representvery strong, strong, medium, and weak, respectively. In terms of100xI/I_(o), the above designations are defined as w=0-15; m=15-60;s=60-80 and vs=80-100.

In certain instances the purity of a synthesized product may be assessedwith reference to its X-ray powder diffraction pattern. Thus, forexample, if a sample is stated to be pure, it is intended only that theX-ray pattern of the sample is free of lines attributable to crystallineimpurities, not that there are no amorphous materials present.

The crystalline compositions of the instant invention may becharacterized by their X-ray powder diffraction patterns and such mayhave one of the X-ray patterns containing the d-spacings and intensitiesset forth in the following Tables. The x-ray pattern for ZS-1, ZS-2,ZS-6, ZS-7, ZS-8, and ZS-11 as reported in U.S. Pat. No. 5,891,417, isas follows:

TABLE 1 ZS X-Ray powder diffraction patterns d (Å) I ZS-1 7.7-8.6 m6.3-7.0 m 5.5-6.3 s 4.7-5.5 m 3.2-4.0 m 2.6-3.4 vs ZS-2 5.8-6.6 m4.2-5.0 w 3.9-4.6 m 2.9-3.7 m 2.5-3.3 vs 2.3-3.0 s ZS-6 6.1-6.9 m4.4-5.1 m 3.4-4.2 m 3.3-4.1 m 2.3-3.1 vs 2.2-3.0 w ZS-7 6.8-7.6 vs5.6-6.4 m 3.7-4.5 m 3.6-4.4 m 2.6-3.4 s-vs 2.5-3.3 m 2.4-3.2 vs ZS-812.0-13.2 vs 3.9-4.7 m 2.8-3.6 m 2.3-3.1 m 2.2-3.0 w 2.1-2.9 w ZS-116.0-6.8 w-m 5.5-6.3 m 5.4-6.2 vs 5.2-6.0 m 2.7-3.5 s 2.5-3.3 m

The x-ray diffraction pattern for the high-purity, high KEC ZS-9 as madein accordance with Example 14 herein (XRD shown in FIG. 12), had thefollowing characteristics d-spacing ranges and intensities:

TABLE 2 ZS-9 d (Å) I 5.9-6.7 m 5.3-6.1 m-s 2.7-3.5 vs 2.0-2.8 w-m1.6-2.4 w

The formation of ZS involves the reaction of sodium silicate andzirconium acetate in the presence of sodium hydroxide and water. Thereaction has typically been conducted in small reaction vessels on theorder of 1-5 Gallons. The smaller reaction vessels have been used toproduce various crystalline forms of ZS including ZS-9. The inventorsrecognized that the ZS-9 being produced in these smaller reactors had aninadequate or undesirably low cation exchange capacity (“CEC”).

The inventors have discovered that the use and proper positioning of abaffle-like structure in relation to the agitator within thecrystallization vessel produces a ZS-9 crystal product exhibitingcrystalline purity (as shown by XRD and FTIR spectra) and anunexpectedly high potassium exchange capacity. In smaller scale reactors(5-gal), cooling coils were positioned within the reactor to provide abaffle-like structure. The cooling coils were not used for heatexchange. Several types of cooling coils are available and the differentdesigns may have some effect on the results presented herein, but theinventors used serpentine-type coils which snake along the inside wallof the reactor vessel.

The inventors found that the crystallization reaction used to produceZS-9 particularly benefited from baffles that when they are properlypositioned relative to the agitator. The inventors initially producedZS-9 with significant levels of undesirable ZS-11 impurity. See FIGS.10-11. This incomplete reaction is believed to have resulted fromsignificant amounts of solids remaining near the bottom of the reactionvessel. These solids near the bottom of the vessel remain even withconventional agitation. When properly positioned, the baffles andagitator improved the reaction conditions by creating forces within thereactor that lift the crystals within the vessel allowing for thenecessary heat transfer and agitation to make a high purity form ofZS-9. In one embodiment, the baffles in combination with the agitatormay be configured such that it provides sufficient lift throughout theentire volume regardless of the size of the reactor used. For example,if the reactor size is enlarged (e.g., 200 liter reactor) and thereaction volume is increased, the baffles will also be resized toaccommodate the new reactor volume. FIGS. 12-13 show XRD and FTIRspectra of high purity ZS-9 crystals. As shown in Table 3 below, thesecrystals exhibit significantly higher levels of potassium exchangecapacity (“KEC”) than the less pure ZS-9 compositions. In an embodimentof the invention, the ZS-9 crystals had a potassium exchange capacity ofbetween 2.7 and 3.7 meq/g, more preferably between 3.05 and 3.35 meq/g.ZS-9 crystals with a potassium exchange capacity of 3.1 meq/g have beenmanufactured on a commercial scale and have achieved desirable clinicaloutcomes. It is expected that ZS-9 crystals with a potassium exchangecapacity of 3.2 meq/g will also achieve desirable clinical outcomes andoffer improved dosing forms. The targets of 3.1 and 3.2 meq/g may beachieved with a tolerance of ±15%, more preferably ±10%, and mostpreferably ±5%. Higher capacity forms of ZS-9 are desirable although aremore difficult to produce on a commercial scale. Such higher capacityforms of ZS-9 have elevated exchange capacities of greater than 3.5meq/g, preferably greater than 4.0 meq/g, more preferably between 4.3and 4.8 meq/g, even more preferably between 4.4 and 4.7 meq/g, and mostpreferably approximately 4.5 meq/g. ZS-9 crystals having a potassiumexchange capacity in the range of between 3.7 and 3.9 meq/g wereproduced in accordance with Example 14 below.

Another unexpected benefit that came from using the reactor having astandard agitator in combination with baffles is that the highcrystalline purity, high potassium exchange capacity ZS-9 crystals couldbe produced without utilizing any seed crystals. Prior attempts atmaking homogenous crystals having high crystalline purity of a singlecrystalline form have utilized seed crystals. The ability to eliminatethe use of seed crystals was therefore an unexpected improvementrelative to prior art processes.

As stated the microporous compositions of this invention have aframework structure of octahedral ZrO₃ units, at least one oftetrahedral SiO₂ units and tetrahedral GeO₂ units, and optionallyoctahedral MO₃ units. This framework results in a microporous structurehaving an intracrystalline pore system with uniform pore diameters,i.e., the pore sizes are crystallographically regular. The diameter ofthe pores can vary considerably from about 3 angstroms and larger.

As synthesized, the microporous compositions of this invention willcontain some of the alkali metal templating agent in the pores. Thesemetals are described as exchangeable cations, meaning that they can beexchanged with other (secondary) A′ cations. Generally, the Aexchangeable cations can be exchanged with A′ cations selected fromother alkali metal cations (K⁺, Na⁺, Rb⁺, Cs⁺), alkaline earth cations(Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺), hydronium ion or mixtures thereof. It isunderstood that the A′ cation is different from the A cation. Themethods used to exchange one cation for another are well known in theart and involve contacting the microporous compositions with a solutioncontaining the desired cation (usually at molar excess) at exchangeconditions. Typically, exchange conditions include a temperature ofabout 25° C. to about 100° C. and a time of about 20 minutes to about 2hours. The use of water to exchange ions to replace sodium ions withhydronium ions may require more time, on the order of eight to tenhours. The particular cation (or mixture thereof) which is present inthe final product will depend on the particular use and the specificcomposition being used. One particular composition is an ion exchangerwhere the A′ cation is a mixture of Na⁺, Ca⁺² and H⁺ ions.

When ZS-9 is formed according to these processes, it can be recovered inthe Na-ZS-9 form. The sodium content of Na-ZS-9 is approximately 12 to13% by weight when the manufacturing process is carried out at pHgreater than 9. The Na-ZS-9 is unstable in concentrations ofhydrochloric acid (HCl) exceeding 0.2 M at room temperature, and willundergo structural collapse after overnight exposure. While ZS-9 isslightly stable in 0.2 M HCl at room temperature, at 37° C. the materialrapidly loses crystallinity. At room temperature, Na-ZS-9 is stable insolutions of 0.1M HCl and/or a pH of between approximately 6 to 7. Underthese conditions, the Na level is decreased from 13% to 2% uponovernight treatment.

The conversion of Na-ZS-9 to H-ZS-9 may be accomplished through acombination of water washing and ion exchange processes, i.e., ionexchange using a dilute strong acid, e.g., 0.1 M HCl or by washing withwater. Washing with water will decrease the pH and protonate asignificant fraction of the ZS, thereby lowering the weight fraction ofNa in the ZS. It may be desirable to perform an initial ion exchange instrong acid using higher concentrations, so long as the protonation ofthe ZS will effectively keep the pH from dropping to levels at which theZS decomposes. Additional ion exchange may be accomplished with washingin water or dilute acids to further reduce the level of sodium in theZS. The ZS made in accordance with the present invention exhibits asodium content of below 12% by weight. Preferably, the sodium contentsis below 9% by weight, more preferably the sodium content is below 6% byweight, more preferably the sodium content is below 3% by weight, morepreferably the sodium content is in a range of between 0.05 to 3% byweight, and most preferably 0.01% or less by weight or as low aspossible. When protonated (i.e., low sodium) ZS is prepared inaccordance with these techniques, the potassium exchange capacity islowered relative to the un-protonated crystals. The ZS prepared in thisway has a potassium exchange capacity of greater than 2.8. In apreferred aspect, the potassium exchange capacity is within the range of2.8 to 3.5 meq/g, more preferably within the range of 3.05 and 3.35meq/g, and most preferably about 3.2 meq/g. A potassium exchangecapacity target of about 3.2 meq/g includes minor fluctuations inmeasured potassium exchange capacity that are expected between differentbatches of ZS crystals.

It has been found that when ZS crystals produced under optimalcrystalline conditions are protonated, the protonation can result in aloss in cation exchange capacity. The inventors have discovered duringscale up of the manufacturing process for ZS-9 that wherecrystallization conditions are less than optimal, the protonation of theproduced ZS crystals results in an increased cation exchange capacityrelative to the unprotonated form. The suboptimal crystallizationconditions result for challenges of maintaining thorough agitation in alarger reaction vessel. For example, when increasing the size of thereaction vessel from a 50 gallons to 125 gallons, ZS-9 crystals with acrystalline impurities were produced. However, assessment of the KECvalues for the protonated H-ZS-9 crystals utilizing this new methodprovided for greater than expected KEC's of greater than 3.1 meq/g, morepreferably in the range of 3.2 to 3.5 meq/g.

The ion exchanger in the sodium form, e.g., Na-ZS-9, is effective atremoving excess potassium ions from a patient's gastrointestinal tractin the treatment of hyperkalemia. When the sodium form is administeredto a patient, hydronium ions replace sodium ions on the exchangerleading to an unwanted rise in pH in the patient's stomach andgastrointestinal tract. Through in vitro tests it takes approximatelytwenty minutes in acid to stabilize sodium ion exchanger.

The hydronium form typically has equivalent efficacy as the sodium formfor removing potassium ions in vivo while avoiding some of thedisadvantages of the sodium form related to pH changes in the patient'sbody. For example, the hydrogenated form has the advantage of avoidingexcessive release of sodium in the body upon administration. This canmitigate edema resulting from excessive sodium levels, particularly whenused to treat acute conditions. Further, patient who are administeredthe hydronium form to treat chronic conditions will benefit from thelower sodium levels, particularly patients at risk for congestive heartfailure. Further, it is believed that the hydronium form will have theeffect of avoiding an undesirable increase of pH in the patient's urine.

The present inventors have found that ZS compositions lacking addedcalcium can serve to withdraw excess calcium from patients which makesthese compositions useful in the treatment of hyperkalemia inhypercalcemic patents as well as for the treatment of hypercalcemia. Thecalcium content of compositions prepared according to the processdescribed in U.S. Provisional Application 61/670,415, incorporated byreference in its entirety, is typically very low—i.e., below 1 ppm. Thepresent inventors have found that treatment of hyperkalemia with thesecompositions is also associated with removal of significant quantitiesof calcium from the patient's body. Therefore, these compositions areparticularly useful for the treatment of hypercalcemic patients orhypercalcemic patients suffering from hyperkalemic.

The compositions of the present invention may be prepared by pre-loadingthe above-described ZS compositions with calcium ions. The pre-loadingof the compositions with calcium results in a composition that will notabsorb calcium when administered to patients. As an alternative, the ZScompositions may also be pre-loaded with magnesium.

The pre-loading of ZS with calcium (and/or magnesium) is accomplished bycontacting the ZS with a dilute solution of either calcium or magnesiumions, preferably having a calcium or magnesium concentration range ofabout 10-100 ppm. The pre-loading step can be accomplishedsimultaneously with the step of exchanging hydronium ions with sodiumions as discussed above. Alternatively, the pre-loading step can beaccomplished by contacting ZS crystals at any stage of their manufacturewith a calcium or magnesium containing solution. Preferably, the ZScompositions comprise calcium or magnesium levels ranging from 1 to 100ppm, preferably from 1 to 30 ppm, and more preferably between 5 and 25ppm.

The pre-loading of ZS does not result in a reduction in potassiumabsorption capacity and therefore does not detract from the use of thesecompositions in the treatment of hyperkalemia. It is believed that dueto their size, calcium and/or magnesium ions do not fully penetrate thepores of the ZS. Rather, the loaded calcium or magnesium remains only onthe surface of the ZS. This added calcium or magnesium results in acomposition that does not absorb calcium or magnesium from the patient'sbody and therefore is preferred for clinical use in the treatment ofhyperkalemia.

In another embodiment, protonated ZS may be linked to hydroxyl-loadedanion exchanger such as zirconium oxide (OH—ZO), which help in theremoval of sodium, potassium, ammonium, hydrogen and phosphate. Withoutbeing bound to a theory, the hydrogen released from the protonated ZSand hydroxide released from OH—ZO combine to form water, thusdiminishing the concentration of “counter-ions” which diminish bindingof other ions. The binding capacity of the cation and anion exchangersshould be increased by administering them together. ZS of this form areuseful for the treatment of many different types of diseases. In oneembodiment, the compositions are used to remove sodium, potassium,ammonium, hydrogen and phosphate from the gut and from the patient withkidney failure.

The ZS-9 crystals have a broad particle size distribution. It has beentheorized that small particles, less than 3 microns in diameter, couldpotentially be absorbed into a patient's bloodstream resulting inundesirable effects such as the accumulation of particles in the urinarytract of the patient, and particularly in the patent's kidneys. Thecommercially available ZS are manufactured in a way that some of theparticles below 1 micron are filtered out. However, it has been foundthat small particles are retained in the filter cake and thatelimination of particles having a diameter less than 3 microns requiresthe use of additional screening techniques.

The inventors have found that screening can be used to remove particleshaving a diameter below 3 microns and that removal of such particles isbeneficial for therapeutic products containing the ZS compositions ofthe invention. Many techniques for particle screening can be used toaccomplish the objectives of the invention, including hand screening,air jet screening, sifting or filtering, floating or any other knownmeans of particle classification. ZS compositions that have been subjectto screening techniques exhibit a desired particle size distributionthat avoids potential complications involving the therapeutic use of ZS.In general, the size distribution of particles is not critical, so longas excessively small particles are removed. The ZS compositions of theinvention exhibit a median particle size greater than 3 microns, andless than 7% of the particles in the composition have a diameter lessthan 3 microns. Preferably, less than 5% of the particles in thecomposition have a diameter less than 3 microns, more preferably lessthan 4% of the particles in the composition have a diameter less than 3microns, more preferably less than 3% of the particles in thecomposition have a diameter of less than 3 microns, more preferably lessthan 2% of the particles in the composition have a diameter of less than3 microns, more preferably less than 1% of the particles in thecomposition have a diameter of less than 3 microns, more preferably lessthan 0.5% of the particles in the composition have a diameter of lessthan 3 microns. Most preferably, none of the particles or only traceamounts have a diameter of less than 3 microns. The median particle sizeis preferably greater than 3 microns and particles reaching a sizes onthe order of 1,000 microns are possible for certain applications.Preferably, the median particle size ranges from 5 to 1000 microns, morepreferably 10 to 600 microns, more preferably from 15 to 200 microns,and most preferably from 20 to 100 microns.

The particle screening can be conducted before, during, or after an ionexchange process such as described above whereby the sodium content ofthe ZS material is lowered below 12%. The lowering of sodium content tobelow 3% can occur over several steps in conjunction with screening orcan occur entirely before or after the screening step. Particles havinga sodium content below 3% may be effective with or without screening ofparticles sizes as described herein.

In addition to screening or sieving, the desired particle sizedistribution may be achieved using a granulation or other agglomerationtechnique for producing appropriately sized particles.

In another embodiment, the ZS compositions may further comprise atoms ormolecules attached onto their surfaces to produced grafted crystals. Thegrafted atoms or molecules are attached to the surface of the ZS,preferably through stable covalent bonds. In one embodiment, anorganosilicate moiety is grafted onto the surface of the ZS compositionthrough reacting active groups such as silanols (≡Si—O—H) on the surfaceof crystals. This may be accomplished, for example by using aproticsolvents. In another embodiment, an alkoxysilane may be grafted andwould require the use of a corresponding alcohol to perform thereaction. Identifying free silanol groups on the surface can donethrough, for example by, Infrared spectroscopy. In another embodiment,if the material to graft lacks of the active groups on their surface,acid washes can be used to promote their formation. Following successfulgrafting, the ZS compositions may further comprise tagging thecomposition with radioactive isotopes, such as but not limited to C orSi. In an alternative embodiment, the ZS compositions may also comprisenon-exchangeable atoms, such as isotopes of Zr, Si, or O, which may beuseful in mass-balance studies.

It is also within the scope of the invention that these microporous ionexchange compositions can be used in powder form or can be formed intovarious shapes by means well known in the art. Examples of these variousshapes include pills, extrudates, spheres, pellets and irregularlyshaped particles. It is also envisioned that the various forms can bepackaged in a variety of known containers. These might include capsules,plastic bags, pouches, packets, sachets, dose packs, vials, bottles, orany other carrying device that is generally known to one of skill in theart.

The microporous ion exchange crystals of this invention may be combinedwith other materials to produce a composition exhibiting a desiredeffect. The ZS compositions may be combined with foods, medicaments,devices, and compositions that are used to treat a variety of diseases.For example, the ZS compositions of the present invention may becombined with toxin reducing compounds, such as charcoal, to expeditetoxin and poison removal. In another embodiment, the ZS crystals mayexist as a combination of two or more forms of ZS of ZS-1 to ZS-11. Inone embodiment, the combination of ZS may comprise ZS-9 and ZS-11, morepreferably ZS-9 and ZS-7, even more preferably ZS-9, ZS-11, and ZS-7. Inanother embodiment of the present invention, the ZS composition maycomprise a blend or mixture of ZS-9, wherein ZS-9 is present at greaterthan at least 40%, more preferably greater than at least 60%, even morepreferably greater than or equal 70%, where the remainder may comprisemixtures of other forms of ZS crystals (i.e., ZS-1 to ZS-11) or otheramorphous forms. In another embodiment, the blend of ZS-9 may comprisegreater than about between 50% to 75% ZS-9 crystals and greater thanabout 25% to about 50% ZS-7 crystals with the remainder being otherforms of ZS crystals, wherein the remainder of the ZS crystals does notinclude ZS-8 crystals.

As stated, these compositions have particular utility in adsorbingvarious toxins from fluids selected from bodily fluids, dialysatesolutions, and mixtures thereof. As used herein, bodily fluids willinclude but not be limited to blood and gastrointestinal fluids. Also bybodily is meant any mammalian body including but not limited to humans,cows, pigs, sheep, monkeys, gorillas, horses, dogs, etc. The instantprocess is particularly suited for removing toxins from a human body.

The zirconium metallates can also be formed into pills or other shapeswhich can be ingested orally and pickup toxins in the gastrointestinalfluid as the ion exchanger transits through the intestines and isfinally excreted. In one embodiment, the ZS compositions may be madeinto wafer, a pill, a powder, a medical food, a suspended powder, or alayered structure comprising two or more ZS. In order to protect the ionexchangers from the high acid content in the stomach, the shapedarticles may be coated with various coatings which will not dissolve inthe stomach, but dissolve in the intestines. In one embodiment, the ZSmay be shaped into a form that is subsequently coated with an entericcoating or embedded within a site specific tablet, or capsule for sitespecific delivery.

As has also been stated, although the instant compositions aresynthesized with a variety of exchangeable cations (“A”), it ispreferred to exchange the cation with secondary cations (A′) which aremore compatible with blood or do not adversely affect the blood. Forthis reason, preferred cations are sodium, calcium, hydronium andmagnesium. Preferred compositions are those containing sodium andcalcium, sodium and magnesium sodium, calcium and hydronium ions,sodium, magnesium, and hydronium ions, or sodium calcium, magnesium, andhydronium ions. The relative amount of sodium and calcium can varyconsiderably and depends on the microporous composition and theconcentration of these ions in the blood. As discussed above, whensodium is the exchangeable cation, it is desirable to replace the sodiumions with hydronium ions thereby reducing the sodium content of thecomposition.

ZS crystals as described in related U.S. application Ser. No.13/371,080, which is incorporated by reference in its entirety, haveincreased cation exchange capacities or potassium exchange capacity.These increased capacity crystals may also be used in accordance withthe present invention. The dosage utilized in formulating thepharmaceutical composition in accordance to the present invention willbe adjusted according to the cation exchange capacities determined bythose of skill in the art. Accordingly, the amount of crystals utilizedin the formulation will vary based on this determination. Due to itshigher cation exchange capacity, less dosage may be required to achievethe same effect.

The compositions of the present invention may be used in the treatmentof diseases or conditions relating to elevated serum potassium levels.These disease may include for example chronic or acute kidney disease,chronic, acute or sub-acute hyperkalemia. To those patients sufferingfrom diseases or conditions with elevated serum potassium levels, theproduct of the present invention is administered at specific potassiumreducing dosages. The administered dose may range from approximately1.25-15 grams (˜18-215 mg/Kg/day) of ZS, preferably 8-12 grams (˜100-170mg/Kg/day), more preferably 10 grams (˜140 mg/Kg/day) three times a day.In another embodiment, the total administered dose of the compositionmay range from approximately 15-45 gram (˜215-640 mg/Kg/day), preferably24-36 grams (˜350-520 mg/Kg/day), more preferably 30 grams (˜400mg/Kg/day). When administered to a subject, the composition of thepresent invention is capable of decreasing the serum potassium levels tonear normal levels of approximately 3.5-5 mmol/L. The molecular sievesof the present product is capable of specifically removing potassiumwithout affecting other electrolytes, (i.e., no hypomagnesemia or nohypocalcemia). The use of the present product or composition isaccomplished without the aid of laxatives or other resins for theremoval of excess serum potassium.

Acute hyperkalemia requires an immediate reduction of serum potassiumlevels to normal or near normal levels. Molecular sieves of the presentinvention which have a KEC in the range of approximately 1.3-2.5 meq/gwould be capable of lowering the elevated levels of potassium to withinnormal range in a period of about 1-8 hours after administration. In oneembodiment, the product of the present invention is capable of loweringthe elevated levels in about at least 1, 2, 4, 6, 8, 10 hours afteradministration. The dose required to reduce the elevated potassiumlevels may be in the range of about 5-15 grams, preferably 8-12 grams,more preferably 10 grams. Molecular sieves having a higher KEC in therange of approximately 2.5-4.7 meq/g would be more efficient inabsorbing potassium. As a result, the dose required to reduce theelevated potassium levels may be in the range of about 1.25-6 grams. Theschedule of dose administration may be at least once daily, morepreferably three times a day.

The treatment of chronic and sub-acute hyperkalemia will requiremaintenance dosing to keep potassium levels near or within normal serumpotassium levels. As such, the administration of the product of thepresent invention will be lower than that prescribed to patientssuffering from acute hyperkalemia. In one embodiment, compositionscomprising molecular sieves having KEC in the range of approximately2.5-4.7 meq/g will be scheduled for a dose in the range of approximately1-5 grams, preferably 1.25-5 grams, preferably 2.5-5 grams, preferably2-4 grams, more preferably 2.5 grams. Compositions comprising molecularsieves having a KEC in the range of approximately 2.5-4.7 meq/g willreceive less and will be scheduled for a dose in the range ofapproximately 0.4-2.5 grams, preferably 0.8-1.6 grams, preferably 1.25-5grams, preferably 2.5-5 grams, more preferably 1.25 grams. Compliance inthis subset of patients is a major factor in maintaining normalpotassium levels. As such, dosing schedule will therefore be animportant consideration. In one embodiment, the dose will be given topatients at least three times a day, more preferably once a day.

The composition or product of the present invention may be formulated ina manner that is convenient for administration. For example, thecomposition of the present invention may be formulated as a tablet,capsule, powder, granule, crystal, packet, or any other dose form thatis generally known to one of skill in the art. The various forms can beformulated as individual dosages comprising between 5-15 grams,preferably 8-12 grams, or more preferably 10 grams for multipleadministrations per day, week or month; or they may be formulated as asingle dosage comprising between 15-45 grams, preferably 24-36 grams, ormore preferably 30 grams. In an alternative embodiment, the individualdosage form can be at least greater than 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,20, 30, or 40 grams. If the dosage form is tablet, it may be formulatedas a granule, granule-like, or as an extended release form. Capsules maybe formulated for administration three times a day, as a sprinkle, anextended release sprinkle, or a dose pack. Powders may be formulated forreconstitution, contained in plastic bags or packets. Those of skill inthe art will recognize that the above description of dosage forms is notlimiting and that other dosage forms for solids may be used toadminister the product or composition of the present invention.

Surprisingly, the administration of the composition of the presentinvention at the specifically described dosing of approximately 10 grams(˜140 mg/Kg/day) three times a day (i.e., 30 grams (˜400 mg/Kg/day)total) is capable of reducing potassium levels in the serum for anextended duration of time. The inventors have found that when theproduct or composition of the present invention is administered at adosage of approximately 10 grams three times a day, the effects oflowering serum potassium levels to within normal levels is sustained for5 days after 2 days of acute therapy. It was expected, however, that theproduct of the present invention would be expelled in a relatively quickmanner.

The ZS of the present invention may be modified and/or combined withother drugs or treatments if multiple conditions or diseases are presentin a subject. For example, in one embodiment a subject may present withboth hyperkalemia and chronic kidney disease, in which Na-ZScompositions may be used. In another embodiment, the ZS compositionsused to treat chronic kidney disease may further comprise sodiumbicarbonate in combination with protonated forms of the ZS. In anotherembodiment, subjects presenting with hyperkalemia and chronic heartfailure may require the use of protonated ZS compositions. In anotherembodiment, the treatment of hyperkalemia and chronic heart disease willrequire no more than 10% sodium present in the ZS, more preferably lessthan 2% sodium.

In other embodiments of the invention, the ZS described herein may befurther combined with activated carbon. The activated carbon has theeffect of attracting organic molecules circulating within the system ofa subject. See, e.g., HSGD Haemosorbents for Medical DeviceApplications, Nikolaev V. G. Presentation, London. As such, thecombination of activated carbon with a ZS will act as a combinationproduct having the ability to remove both excess potassium, and organicmolecules. The activated carbon will comprise a multiplicity ofadsorption pores of ranging from about 8 angstroms to about 800angstroms in diameter, preferably at least about 50 angstroms indiameter. The ZS combined with activated carbon of the present inventionwill be useful in the treatment of many diseases and/or conditionsrequiring the removal of excess organic materials, such as but notlimited to, lipids, proteins, and toxins. For example, the carboncontaining ZS compositions of the present invention will be useful inthe removal of pyrimidines, methylguanidines, guanidines,o-hydroxyhippuric acid, p-hydroxyhippuric acid, parathormone, purines,phenols, indols, pesticides, carcinogenic heterocyclic amines,conjugates of ascorbic acids, trihalomethanes, dimethylarginine,methylamines, organic chloramines, polyamines, or combinations thereof.The activated carbon combined with ZS will also be useful in adsorbingelevated levels of bile acids, albumin, ammonia, creatinine andbilirubin. To further improve the adsorption of activated carbon withcoated ZS, the composition may be further coated with an albumin layer,a lipid layer, a DNA layer, a heparin layer, resulting in additionaladsorption efficiencies ranging from about 12% to about 35%.

The activated carbon and ZS compositions will be useful in treating asubject presenting with multiple diseases or conditions, such ashyperkalemia, acute and chronic esogastritis, acute and chronicintestinal catarrhus, hyperacid gastritis, summer diarrhea, catarrhaljaundice, food related toxicoinfections, kidney disease, dysentery,choloera, typhoid, intestinal bacilli-carrier, heartburn, nausea, acuteviral hepatitis, chronic active hepatitis and cirrhosis, concomitanthepatitis, mechanical jaundice, hepato-renal failure, hepatic coma, orcombinations thereof.

In another embodiment, the ZS compositions described herein may be usedin a variety of methods comprising administering to a subject in needthereof a composition described herein to remove excess levels ofpotassium. In another embodiment of the present invention, the methodmay include the administration of a combination of the ZS describedherein and may further comprise additional compositions to aid in theremoval of potassium while simultaneously removing other substances,such as but not limited to toxins, proteins, or ions, from the subject.

In order to more fully illustrate the invention, the following examplesare set forth. It is to be understood that the examples are only by wayof illustration and are not intended as an undue limitation on the broadscope of the invention as set forth in the appended claims.

EXAMPLE 1

A solution was prepared by mixing 2058 g of colloidal silica (DuPontCorp. identified as Ludox™ AS-40), 2210 g of KOH in 7655 g H₂O. Afterseveral minutes of vigorous stirring 1471 g of a zirconium acetatesolution (22.1 wt. % ZrO₂) were added. This mixture was stirred for anadditional 3 minutes and the resulting gel was transferred to astainless steel reactor and hydrothermally reacted for 36 hours at 200°C. The reactor was cooled to room temperature and the mixture was vacuumfiltered to isolate solids which were washed with deionized water anddried in air.

The solid reaction product was analyzed and found to contain 21.2 wt. %Si, 21.5 wt. % Zr, K 20.9 wt. % K, loss on ignition (LOI) 12.8 wt. %,which gave a formula of K_(2.3)ZrSi_(3.2)O_(9.5)*3.7H₂O. This productwas identified as sample A.

EXAMPLE 2

A solution was prepared by mixing 121.5 g of colloidal silica (DuPontCorp. identified as Ludox® AS-40), 83.7 g of NaOH in 1051 g H₂O. Afterseveral minutes of vigorous stirring 66.9 g zirconium acetate solution(22.1 wt. % ZrO₂) was added. This was stirred for an additional 3minutes and the resulting gel was transferred to a stainless steelreactor and hydrothermally reacted with stirring for 72 hours at 200° C.The reactor was cooled to room temperature and the mixture was vacuumfiltered to isolate solids which were washed with deionized water anddried in air.

The solid reaction product was analyzed and found to contain 22.7 wt. %Si, 24.8 wt. % Zr, 12.8 wt. % Na, LOI 13.7 wt. %, which gives a formulaNa_(2.0)ZrSi_(3.0)O_(9.0)*3.5H₂O. This product was identified as sampleB.

EXAMPLE 3

A solution (60.08 g) of colloidal silica (DuPont Corp. identified asLudox® AS-40) was slowly added over a period of 15 minutes to a stirringsolution of 64.52 g of KOH dissolved in 224 g deionized H₂O. This wasfollowed by the addition of 45.61 g zirconium acetate (Aldrich 15-16 wt.% Zr, in dilute acetic acid). When this addition was complete, 4.75 ghydrous Nb₂O₅ (30 wt. % LOI) was added and stirred for an additional 5minutes. The resulting gel was transferred to a stirred autoclavereactor and hydrothermally treated for 1 day at 200° C. After this time,the reactor was cooled to room temperature, the mixture was vacuumfiltered, the solid washed with deionized water and dried in air.

The solid reaction product was analyzed and found to contain 20.3 wt. %Si, 15.6 wt. % Zr, 20.2 wt. % K, 6.60 wt. % Nb, LOI 9.32 wt. %, whichgive a formula of K_(2.14)Zr_(0.71)Nb_(0.29) Si₃O_(9.2)*2.32H₂O.Scanning Electron (SEM) of a portion of the sample, including EDAX of acrystal, indicated the presence of niobium, zirconium, and siliconframework elements. This product was identified as sample C.

EXAMPLE 4

To a solution prepared by mixing 141.9 g of NaOH pellets in 774.5 g ofwater, there were added 303.8 g of sodium silicate with stirring. Tothis mixture there were added dropwise, 179.9 g of zirconium acetate(15% Zr in a 10% acetic acid solution). After thorough blending, themixture was transferred to a Hastalloy™ reactor and heated to 200° C.under autogenous pressure with stirring for 72 hours. At the end of thereaction time, the mixture was cooled to room temperature, filtered andthe solid product was washed with a 0.001 M NaOH solution and then driedat 100° C. for 16 hours. Analysis by x-ray powder diffraction showedthat the product was pure ZS-11.

EXAMPLE 5

To a container there was added a solution of 37.6 g NaOH pelletsdissolved in 848.5 g water and to this solution there were added 322.8 gof sodium silicate with mixing. To this mixture there were addeddropwise 191.2 g of zirconium acetate (15% Zr in 10% acetic acid). Afterthorough blending, the mixture was transferred to a Hastalloy™ reactorand the reactor was heated to 200° C. under autogenous conditions withstirring for 72 hours. Upon cooling, the product was filtered, washedwith 0.001 M NaOH solution and then dried at 100° C. for 16 hours. X-raypowder diffraction analysis showed the product to be ZS-9 (i.e., acomposition that is predominately ZS-9 crystalline form).

EXAMPLE 6

Approximately 57 g (non-volatile-free basis, lot 0063-58-30) of Na-ZS-9was suspended in about 25 mL of water. A solution of 0.1N HCl was addedgradually, with gentle stirring, and pH monitored with a pH meter. Atotal of about 178 milliliters of 0.1 N HCl was added with stirring, themixture filtered then further rinsed with additional 1.2 liters 0.1 NHCl washes. The material was filtered, dried and washed with DI water.The pH of the resulting material was 7.0. The H-ZS-9 powder resultingfrom this three batch-wise ion exchange with 0.1 N HCl has <12% Na.

As illustrated in this example, batch-wise ion exchange with a dilutestrong acid is capable of reducing the sodium content of a NA-ZS-9composition to within a desired range.

EXAMPLE 7

Approximately 85 gram (non-volatile-free basis, lot 0063-59-26) ofNa-ZS-9 was washed with approximately 31 Liters of DI water at 2 Literincrements over 3 days until the pH of the rinsate reached 7. Thematerial was filtered, dried and washed with DI water. The pH of theresulting material was 7. The H-ZS-9 powder resulting from batch-wiseion exchange and water wash has <12% Na.

As illustrated in this example, water washing is capable of reducing thesodium content of a NA-ZS-9 composition to within a desired range.

EXAMPLE 8

Separate batches of ZS-9 crystals were analyzed using light scatterdiffraction techniques. The particle size distribution and othermeasured parameters are shown in FIGS. 2-4. The d(0.1), d(0.5), andd(0.9) values represent the 10%, 50%, and 90% size values. Thecumulative particle size distribution is shown in FIG. 4-6. As can beseen from the following figures, the cumulative volume of particleshaving a diameter below 3 microns ranges from approximately 0.3% toapproximately 6%. In addition, different batches of ZS-9 have differentparticle size distributions with varying levels of particles having adiameter of less than 3 microns.

EXAMPLE 9

Crystals of ZS-9 were subject to screening to remove small diameterparticles. The resulting particle size distribution of the ZS-9 crystalsscreened using different size screens was analyzed. As illustrated inthe following figures, the fraction of particles having a diameter below3 microns can be lowered and eliminated using an appropriate mesh sizescreen. Without screening, approximately 2.5% percent of the particleshad a diameter of below 3 microns. See FIG. 5. Upon screening with a 635mesh screen, the fraction of particles having a diameter below 3 micronswas reduced to approximately 2.4%. See FIG. 6. Upon screening with a 450mesh screen, the fraction of particles having a diameter below 3 micronswas reduced further to approximately 2%. See FIG. 7. When a 325 meshscreen is used, the fraction of particles having a diameter below 3microns is further reduced to approximately 0.14%. See FIG. 8. Finally,a 230 mesh screen reduces the fraction of particles below 3 microns to0%. See FIG. 9.

The screening techniques presented in this example illustrate thatparticle size distributions may be obtained for ZS-9 that provide littleor no particles below 3 microns. It will be appreciated that ZS-9according to Example 5 or H-ZS-9 according to Examples 6 and 7 may bescreened as taught in this example to provide a desired particle sizedistribution. Specifically, the preferred particle size distributionsdisclosed herein may be obtained using the techniques in this examplefor both ZS-9 and H-ZS-9.

EXAMPLE 10

A 14-Day repeat dose oral toxicity study in Beagle Dogs with Recoverywas conducted. This GLP compliant oral toxicity study was performed inbeagle dogs to evaluate the potential oral toxicity of ZS-9 whenadministered at 6 h intervals over a 12 h period, three times a day, infood, for at least 14 consecutive days. In the Main Study ZS-9 wasadministered to 3/dogs/sex/dose at dosages of 0 (control), 325, 650 or1300 mg/kg/dose. An additional 2 dogs/sex/dose, assigned to the RecoveryStudy, received 0 or 1300 mg/kg/dose concurrently with the Main studyanimals and were retained off treatment for an additional 10 days. Acorrection factor of 1.1274 was used to correct ZS-9 for water content.Dose records were used to confirm the accuracy of dose administration.

During the acclimation period (Day −7 to Day −1) dogs were trained toeat 3 portions of wet dog chow at 6 h intervals. During treatment therequisite amount of test article (based on the most recently recordedbody weight) was mixed with ˜100 g of wet dog food and offered to thedogs at 6 h intervals. Additional dry food was offered followingconsumption of the last daily dose. Each dog received the same amount ofwet dog feed. Body weights were recorded at arrival and on Days −2, −1,6, 13 and 20. Clinical observations were performed twice daily duringthe acclimation, treatment and recovery periods. Wet and dry foodconsumption was measured daily during the treatment period. Blood andurine samples for analysis of serum chemistry, hematology, coagulationand urinalysis parameters were collected pretest (Day −1) and Day 13.Ophthalmologic examinations were performed pretest (Day −6/7) and on Day7 (females) or 8 (males). Electrocardiographic assessments wereperformed pretest (Day −1) and on Day 11. At study termination (Day14—Main Study and Day 24—Recovery Study), necropsy examinations wereperformed, protocol specified organ weights were weighed, and selectedtissues were microscopically examined.

Oral administration of 325, 650 and 1300 mg ZS-9/kg/dose with food,three times a day at 6 h intervals over a 12-hour period for 14 days waswell tolerated. Clinical signs were limited to the observation of whitematerial, presumed to be test article, in the feces of some dogs at the325 mg/kg/dose and in all animals receiving ≧650 mg/kg/dose during thesecond week of treatment. There were no adverse effects on body weight,body weight change, food consumption, hematology and coagulationparameters or ophthalmoscopic and ECG evaluations.

There were no macroscopic findings associated with administration ofZS-9. Microscopically, minimal to mild focal and/or multifocalinflammation was observed in the kidneys of treated animals but not inControl animals. The lesions had similar incidence and severity at 650and 1300 mg/kg and were less frequent and severe at 325 mg/kg. In somedogs the inflammation was unilateral rather than bilateral and in somecases was associated with inflammation in the urinary bladder and originof the ureter. Taken together these observations suggest that factorsother than direct renal injury, such as alterations in urine compositionof ZS-9-treated dogs may have resulted in increased susceptibility tosubclinical urinary tract infections, even though no microorganisms wereobserved in these tissues. In recovery animals the inflammation wascompletely resolved in females and partly resolved in males suggestingthat whatever the cause of the inflammation it was reversible followingcessation of dosing.

The increased incidence of mixed leukocyte inflammation observed inBeagle dogs treated with ZS-9 is summarized below.

Summary of Inflammation in Kidneys Terminal Necropsy (TN): Day 14 Dose 0325 650 1,300 mg/kg mg/kg mg/kg mg/kg Sex M F M F M F M F Number ofAnimals 3 3 3 3 3 3 3 3 Left Kidney Incidence 0/3 0/3 0/3 2/3 2/3 3/33/3 3/3 minimal 0/3 0/3 0/3 2/3 2/3 2/3 3/3 1/3 mild 0/3 0/3 0/3 0/3 0/31/3 0/3 2/3 Right Incidence 0/3 0/3 1/3 1/3 2/3 3/3 2/3 2/3 Kidneyminimal 0/3 0/3 1/3 1/3 2/3 1/3 2/3 0/3 mild 0/3 0/3 0/3 0/3 0/3 2/3 0/32/3 Both Incidence 0/6 0/6 1/6 3/6 4/6 6/6 5/6 5/6 Kidneys minimal 0/60/6 1/6 3/6 4/6 3/6 5/6 1/6 mild 0/6 0/6 0/6 0/6 0/6 3/6 0/6 4/6 Sum ofSeverity Scores 0 0 2 3 4 9 5 9 0 5 13 14 Mean Group Severity 0.00 0.832.17 2.33 Scores

Minimal acute urinary bladder inflammation and unidentified crystalswere also observed in the renal pelvis and urine of females dosed at 650mg/kg/dose as summarized below

Summary of Crystals observed at the 650 mg/kg/dose Animal No 4420 44214422 Unidentified crystals + − + in urine Crystals in renal pelvis − + −Urinary bladder + + − acute inflammation

Crystals were not identified in group 2 or 4 females or in any ZS-9treated males.

In both studies it was noted that urinary pH was elevated compared tocontrol and it was postulated that the change in urinary pH and/orurinary composition affected urine solute solubility resulting incrystal formation that caused urinary tract irritation and/or increasedsusceptibility to urinary tract infections (UTIs).

The description of the urinary crystals (long thin spiky clusters)coupled with the particle size profile and insolubility of test articlemake it very unlikely that these crystals are ZS-9.

EXAMPLE 11

Crystals of ZS-9 are prepared and designated “ZS-9 Unscreened.”Screening in accordance with the procedures of Example 10 is conductedon a sample of ZS-9 crystals and the screened sample is designated“ZS-9>5 μm.” Another sample of Crystals of ZS-9 undergo an ion exchangein accordance with the procedures of Example 6 above and are thenscreened in accordance with the procedures of Example 10. The resultingH-ZS-9 crystals are designated “ZS-9+>5 μm.”

The following 14-day study is designed to show the effect of particlesize and particle form on the urinary pH and presence of crystals in theurine. The compounds above are administered to beagles orally by mixingwith wet dog food. The regimen is administered 3 times a day at 6 hourintervals over a 12 hour period in the following manner:

STUDY DESIGN Group mg/kg/dose* Female Control 0 3 ZS-9 Unscreened 600 3ZS-9 >5 μm 600 3 ZS-9 + >5 μm 600 3 ZS-9 Unscreened 100 3 ZS-9 >5 μm 1003 ZS-9 + >5 μm 100 3 NaHCO₃ 50 3 Total number of dogs 24 females Age 5months of age on arrival Acclimation ≧10 days Test Article FormulationMixed with wet dog food Test article administration Within 30 minutes ofadministration Dose Formulation Analysis Dose records will be used toconfirm dosing. Weight of any remaining wet food will be recorded.*uncorrected for water ZS-9+ = pH neutral crystalThe following table outlines the observations, toxicokinetic evaluation,laboratory investigation (hematology, urinalysis), and terminalprocedures.

OBSERVATIONS Mortality & Signs of Twice daily (after treatment andevening) ill health or reaction including feces assessment to treatmentDetailed Exam During acclimation, weekly on study Body Weights Arrival,Day −1, Day 7 and 14 Food Consumption Daily (Wet and Dry food)Ophthalmoloscopy None TOXICOKINETIC (FOR POTENTIAL ZR ANALYSIS) 3 × 1 mlwhole Day −1: Pre-dose blood/sample with Day 13: Pre-dose and 4 h post2^(nd) dose sample weights recorded LABORATORY INVESTIGATIONSHematology/Clinical Pretreatment and during Weeks 1 and 2 on studychemistry (see list) Urinalysis Pretreatment and during Weeks 1 and 2 onstudy (see list) (Metabolic cage, urine sample to be kept cool)Remaining urine aliquoted and retained frozen for possible future Zranalysis Terminal Procedures Necropsy All animals regardless of mode ofdeath. All tissues collected into NBF (see list) Histopathology Urinarytract only (Kidney and bladder)

During this study in female dogs, the test articles, ZS-9 unscreened,ZS-9>5 μm, and ZS-9+>5 μm, were administered three times daily at 6 hourintervals over a 12-hour period for 14 consecutive days via dietaryconsumption utilizing a wet food vehicle. The dose levels were 100 or600 mg/kg/dose.

All animals survived the 14-day administration period. There were notest article-related changes in mortality, body weight, body weightgain, organ weights, macroscopic findings, or on clinical chemistry orblood gas parameters. ZS-9 related findings were limited to an increasein the fractional excretion of sodium and an increase in urinary pH inanimals receiving screened or unscreened ZS-9 at a dose of 6000mg/kg/dose, and decreases in the fractional excretion of potassium andthe urinary urea nitrogen/creatinine ratio in animals dosed at 600mg/kg/dose ZS-9 unscreened, ZS-9>5 μm, and ZS-9+>5 μm.

Statistically significant increases in urinary pH compared to Control inanimals treated with 600 mg/kg/dose of ZS-9 unscreened and ZS-9>5 μm,that was not observed at the 100 mg/kg/dose or in animals treated with600 mg/kg/dose of ZS-9+>5 μm. Mean urinary pH in these animals increasedfrom 5.33 to ˜7.67 on Day 7 and from 5.83 to 7.733 on Day 13. The lackof effect on urinary pH in animals treated with 600 mg/kg/dose ofprotonated ZS-9 (ZS-9+>5 μm) suggests that the increase in the urinarypH in animals treated with the higher dose of sodium loaded ZS-9 (ZS-9unscreened and ZS-9>5 μm) was a result of gastrointestinal hydrogenabsorption.

All differences found in urine volume and specific gravity wereconsidered within an acceptable range for normal biological and/orprocedure-related variability. There were some variations betweentreatment groups among biochemical (protein, ketones, etc.) andmicroscopic (crystals, blood cells, etc.) urinary components that werealso considered within an acceptable range for biological and/orprocedure-related variability. Triple phosphate crystals (magnesiumammonium phosphate) were observed in most animals at all studyintervals, rarely calcium oxalate dihydrate crystals were also observedin a few animals. Both of these crystal types are considered a normalfinding in dogs. No patterns were observed to suggest that any of thecrystals observed were treatment or test article-related in any animal.No unidentified crystals were observed in the urinary sediment of anyanimal.

On Days 7 and 13 the fractional excretion of sodium was increasedrelative to predose intervals in all groups including controls. Animalsreceiving 600 mg/kg/dose ZS-9 unscreened, ZS-9>5 μm, and ZS-9+>5 μmtended to have increases that were slighter greater (up to 116% relativeto controls) than those seen in other treatment groups or among thecontrol animals. The increases observed in these three groupsoccasionally reached magnitudes that were considered above expectedranges and were attributed to the test article. No discernibledifferences between the changes observed in these three groups could beidentified. There was no difference in the fractional excretion ofsodium in animals treated with 600 mg/kg/dose of the protonated ZS-9.These changes were attributed to the test article and were notconsidered toxicologically adverse.

Significant decreases in the fractional excretion of potassium, relativeto Control, were observed in animals treated with 600 mg/kg/dose ZS-9unscreened, ZS-9>5 μm, and ZS-9+>5 μm, and 100 mg/kg/dose ZS-9>5 μm onDays 7 and 13. Most of these values reached statistical significancerelative to controls on Days 7 and 13. These decreases were attributedto the pharmacological effect of the test article.

On Days 7 and 13 urea nitrogen/creatinine ratio was mildly increasedrelative to predose intervals in all groups including controls. Therewere mild decreases in urea nitrogen/creatinine ratios on Days 7 and 13in animals receiving 600 mg/kg/dose ZS-9 unscreened, ZS-9>5 μm, andZS-9+>5 μm relative to controls (up to 26%). Most of the changesobserved in these four groups reached statistical significance comparedto controls for Days 7 and 13 although group mean values did not differappreciably when compared to their respective pretest values. Thesefindings were considered test article-related. Although there wereoccasional statistically significant differences among other endpoints,no test article-related effects on creatinine clearance,calcium/creatinine ratio, magnesium/creatinine ratio, or urineosmolality were identified in any treatment group.

Test article related microscopic findings in the kidney were observed atthe 600 mg/kg/dose. The most common findings were minimal to mild mixedleukocyte infiltrates (lymphocytes, plasma cells, macrophages and/orneutrophils), and minimal to mild renal tubular regeneration (slightlydilated tubules lined by attenuated epithelial cells, epithelial cellswith plump nucleus and basophilic cytoplasm). Minimal pyelitis(infiltration of neutrophils, lymphocytes and plasma cells in thesubmucosa of the renal pelvis) and minimal renal tubulardegeneration/necrosis (tubules lined by hypereosinophilic cells witheither pyknotic or karyorrhectic nucleus and containing sloughedepithelial cells and/or inflammatory cells in the lumen) were observedin ⅓ dogs receiving 600 mg/kg/dose ZS-9 unscreened and ⅓ dogs receiving600 mg/kg/dose ZS-9>5 μm. Minimal pyelitis and mixed leukocyteinfiltration in the urethra or ureter were also present in some dogsgiven ZS-9>5 μm.

The changes in the kidney were mostly present in the cortex andoccasionally in the medulla with a random, focal to multifocal (up to 4foci) distribution. These foci were variably sized, mostly irregular,occasionally linear (extending from the outer cortex to the medulla),and involved less than 5% of the kidney parenchyma in a given section.Most of these foci consisted of minimal to mild infiltration of mixedleukocytes with minimal to mild tubular regeneration, some foci had onlyminimal to mild tubular regeneration without the mixed leukocyteinfiltrate. A few of these foci (two dogs given 600 mg/kg/dose ZS-9unscreened and one dog given 600 mg/kg/dose ZS-9>5 μm) contained a smallnumber of tubules with degeneration/necrosis. Pyelitis was present infour dogs (one given ZS-9 unscreened 600 mg/kg/dose and three dogs givenZS-9>5 μm at 600 mg/kg/dose).

The infiltration of mixed leukocytes was also present in the submucosaof both ureters in dogs given 600 mg/kg/dose ZS-9>5 μm and the submucosaof the urethra in animals given 600 mg/kg/dose ZS-9 unscreened, 600mg/kg/dose ZS-9>5 μm. The incidence and/or severity of mixed leukocyteinfiltrates in the kidney parenchyma were higher in dogs with pyelitiscompared to the dogs without pyelitis. The presence of pyelitis and/orthe mixed leukocyte infiltrates in the urethra and ureters in some dogsand the multifocal, random distribution of kidney findings withinflammatory infiltrates are reminiscent of an ascending urinary tractinfection and suggest that the kidney findings at the 600 mg/kg/dose arelikely an indirect effect of the test article.

In dogs given ZS-9 unscreened at 600 mg/kg/dose, kidneys in two of thethree dogs were affected with one or more of the aforementionedfindings. All three dogs given ZS-9>5 μm at 600 mg/kg/dose had kidneylesions including pyelitis and mixed leukocyte infiltrates in thesubmucosa of urethra or ureters. Dogs given ZS-9+>5 μm at 600mg/kg/dose, minimal mixed leukocyte infiltrate with tubular regenerationwas present in only the left kidney in one dog while another dog had afew foci of minimal tubular regeneration.

Test article-related findings (direct or indirect) were not present infemale dogs given ZS-9 unscreened at 100 mg/kg/dose (ZS-9, ZS-9>5 μm,ZS-9+>5 μm). An occasional focus or two of minimal tubular regenerationwere present in three of the animals without an evidence of mixedleukocyte infiltrate or tubular degeneration/necrosis. Similarfocus/foci of tubular regeneration were also present in a control femaledog. The foci of tubular regeneration observed in female dogs givenlower doses of ZS-9 unscreened were slightly smaller and were notassociated with either mixed leukocyte infiltrates or tubulardegeneration/necrosis. There was no evidence of crystals in any of thesections examined. Tubular mineralization in the papilla and glomerularlipidosis are background findings in beagle dogs and were not consideredtest article-related.

ZS-9 unscreened, ZS-9>5 μm, and ZS-9+>5 μm at the 600 mg/kg/dose hadminimal to mild mixed leukocyte infiltrates in the kidney sometimesassociated with minimal to mild renal tubular regeneration, andoccasionally minimal renal tubular degeneration/necrosis, minimal mixedleukocyte infiltrates in ureter and/or urethra and minimal pyelitis indogs dosed with ZS-9 unscreened and ZS-9>5 μm.

The lack of increased urinary pH in dogs treated with 600 mg/kg/doseZS-9+>5 μm coupled with the reduced incidence of microscopic findings inthese dogs and dogs treated with 600 mg/kg/dose ZS-9 unscreenedsupplemented with potassium suggest that elevated urinary pH and/orremoval of potassium due to the pharmacological action of the testarticle, may have increased susceptibility to the background insult fromurinary crystals and bacteria.

Based on these results, the no-observable-effect-level (NOEL) was 100mg/kg/dose ZS-9 unscreened, ZS-9>5 μm, and ZS-9+>5 μm. Theno-observable-adverse-effect-level (NOAEL) was established for ZS-9unscreened at 600 mg/kg/dose, screened ZS-9 (ZS-9>5 μm) at 600mg/kg/dose, and screened and protonated ZS-9 (ZS-9+>5 μm) at 600mg/kg/dose.

EXAMPLE 12

ZS-9 crystals were prepared by reaction in a standard 5-Gcrystallization vessel.

The reactants were prepared as follows. A 22-L Morton flask was equippedwith an overhead stirrer, thermocouple, and an equilibrated additionfunnel. The flask was charged with deionized water (3.25 L). Stirringwas initiated at approximately 100 rpm and sodium hydroxide (1091 gNaOH) was added to the flask. The flask contents exothermed as thesodium hydroxide dissolved. The solution was stirred and cooled to lessthan 34° C. Sodium silicate solution (5672.7 g) was added. To thissolution was added zirconium acetate solution (3309.5 g) over 43minutes. The resulting suspension was stirred for another 22 minutes.Seed crystals of ZS-9 (223.8 g) were added to the reaction vessel andstirred for approximately 17 minutes.

The mixture was transferred to a 5-G Parr pressure vessel with the aidof deionized water (0.5 L). The vessel had smooth walls and a standardagitator. The reactor did not have a cooling coil present. The vesselwas sealed and the reaction mixture was stirred at approximately 275-325rpm and heated to 185+/−10° C. over 4 hours, then held at 184-186° C.and soaked for 72 hours. Finally, the reactants were then cooled to 80°C. over 12.6 hours. The resulting white solid was filtered with the aidof deionized water (18 L). The solids were washed with deionized water(125 L) until the pH of the eluting filtrate was less than 11 (9.73).The wet cake was dried in vacuo (25 inches Hg) for 48 hours at 95-105°C. to give 2577.9 g (107.1%) of ZS-9 as a white solid.

The XRD plot of the ZS-9 obtained in this example is shown in FIG. 10.The FTIR plot of this material is shown in FIG. 11. These XRD and FTIRspectra are characterized by the presence of absorption peaks typicallyassociated with the ZS-11 crystalline form. In addition, the peaks thatare associated with ZS-9 exhibit significant spreading due to crystalimpurities (e.g. the presence of ZS-11 crystals in a ZS-9 composition).For example, the FTIR spectra shows significant absorption around 764and 955 cm⁻¹. The XRD plot for this example exhibits significant noiseand poorly defined peaks at 2-theta values of 7.5, 32, and 42.5.

EXAMPLE 13

In this example ZS-9 crystals were protonated.

To a 100 L reaction vessel deionized water is charged (15.1 L) withvacuum and agitation (60-100 rpm). ZS-9 crystals (2.7 kg) were added tothe 100 L vessel containing deionized water and allowed to reaction fora period of 5-10 minutes. Initial pH readings were recorded.

In a separate 50 L carboy, a hydrochloric acid solution is preparedcomprising the steps of charging the carboy with deionized water (48 L)followed by hydrochloric acid (600 ml). To the 100 L reaction vessel,the hydrochloric acid solution is charged over a period of 1.5-2 hours.Hydrochloric acid solution was added to the reaction mixture until thepH reached a range of approximately 4.45-4.55. The reaction mixture wascontinually mixed for an additional period of 30-45 minutes. If the pHwas greater than 4.7, additional hydrochloride solution was added untilthe pH was in the range of approximately 4.45-4.55. The reaction wasallowed to stir for an additional 15-30 minutes.

The protonated ZS-9 crystals were filtered through Buchner funnel fittedwith a 2 micron stainless steel mesh screen of approximately 18 inchesin diameter. The filter cake formed was rinsed three times withapproximately 6 L of deionized water to remove any excess hydrochloricacid. The filter cake containing the protonated crystals were dried inan vacuum oven at approximately 95-105° C. for a period of 12-24 hours.Drying was continued until the percent difference in net weight loss isless than 2% over greater than a 2 hour period. Once the productachieved appropriate dryness, the crystals were samples for quality.

EXAMPLE 14

High capacity ZS-9 crystals were prepared in accordance with thefollowing representative example.

The reactants were prepared as follows. A 22-L Morton flask was equippedwith an overhead stirrer, thermocouple, and an equilibrated additionfunnel. The flask was charged with deionized water (8,600 g, 477.37moles). Stirring was initiated at approximately 145-150 rpm and sodiumhydroxide (661.0 g, 16.53 moles NaOH, 8.26 moles Na20) was added to theflask. The flask contents exothermed from 24° C. to 40° C. over a periodof 3 minutes as the sodium hydroxide dissolved. The solution was stirredfor an hour to allow the initial exotherm to subside. Sodium silicatesolution (5.017 g, 22.53 mole SO2, 8.67 moles Na20) was added. To thissolution, by means of the addition funnel, was added zirconium acetatesolution (2,080 g, 3.76 moles Zr02) over 30 min. The resultingsuspension was stirred for an additional 30 min.

The mixture was transferred to a 5-G Parr pressure vessel Model 4555with the aid of deionized water (500 g, 27.75 moles). The reactor wasfitted with a cooling coil having a serpentine configuration to providea baffle-like structure within the reactor adjacent the agitator. Thecooling coil was not charged with heat exchange fluid as it was beingused in this reaction merely to provide a baffle-like structure adjacentthe agitator.

The vessel was sealed and the reaction mixture was stirred atapproximately 230-235 rpm and heated from 21° C. to 140-145° Cover 7.5hours and held at 140-145° C. for 10.5 hours, then heated to 210-215° C.over 6.5 hours where the maximum pressure of 295-300 psi was obtained,then held at 210-215° C. for 4 1.5 hours. Subsequently, the reactor wascooled to 45° C. over a period of 4.5 hours. The resulting white solidwas filtered with the aid of deionized water (1.0 KG). The solids werewashed with deionized water (40 L) until the pH of the eluting filtratewas less than 11 (10.54). A representative portion of the wet cake wasdried in vacuo (25 inches Hg) overnight at 100° C. to give 1.376 g(87.1%) of ZS-9 as a white solid.

The XRD plot of the ZS-9 obtained is shown in FIG. 12. The FTIR plot ofthis material is shown in FIG. 13. These XRD and FTIR spectra, whencompared to those for Example 12 (FIGS. 10-11), exhibitedwell-delineated peaks without spreading and the absence of peaksassociated with crystalline forms other than ZS-9 (e.g., ZS-11 peaks).This example illustrates how the presence of a baffle-like structurewithin the reactor drastically and unexpectedly improves the quality ofthe thus obtained crystals. Although not wishing to be bound by theory,the inventors understand that baffles provide added turbulence whichlifts the solids (i.e., crystals) and results in a more even suspensionof crystals within the reaction vessel while the reaction is ongoing.This improved suspension allows for more complete reaction to thedesired crystalline form and reduces the presence of unwantedcrystalline forms of ZS in the end product.

EXAMPLE 15

The KEC of ZS (ZS-9) was determined according to the following protocol.

This test method used a HPLC capable of gradient solvent introductionand cation exchange detection. The column was an IonPac CS12A,Analytical (2×250 mm). The flow rate was 0.5 mL/minute with a run timeof approximately 8 minutes. The column temperature was set to 35° C. Theinjection volume was 10 μL and the needle wash was 250 μL. The pump wasoperated in Isocratic mode and the solvent was DI water.

A stock standard was prepared by accurately weighing and recording theweight of about 383 mg of potassium chloride (ACS grade), which wastransferred into a 100-rnL plastic volumetric flask. The material wasdissolved and diluted to volume with diluent followed by mixing. Thestock standard had a K⁺ concentration of 2000 ppm (2 mg/mL). Sampleswere prepared by accurately weighing, recording, and transferring about112 mg of ZS-9 into a 20 mL plastic vial. 20.0 mL of the 2000 ppmpotassium stock standard solution was pipetted into the vial and thecontainer was closed. The sample vials were placed onto a wrist actionshaker and were shook for at least 2 hours but not more than 4 hours.The sample preparation solution was filtered through a 0.45 pm PTFEfilter into a plastic container. 750 pL of the sample solution wastransferred into a 100-mL plastic volumetric flask. The sample wasdiluted to volume with DI water and mixed. The initial K⁺ concentrationwas 15 ppm (1 SpgImL).

The samples were injected into the HPLC. FIG. 14 shows an example of theblank solution chromatogram. FIG. 15 shows an example of the assaystandard solution chromatogram. FIG. 16 shows an exemplary samplechromatogram. The potassium exchange capacity was calculated using thefollowing formula:

${KEC} = \frac{\frac{\left( {{IC} - {FC}} \right) \times V}{{Eq}\mspace{14mu}{{wt}.}}}{{{Wt}._{SPL}} \times \frac{\left( {{100\mspace{11mu}\%} - {\%\mspace{14mu}{Water}}} \right)}{100\mspace{11mu}\%} \times \frac{1\; g}{1000\mspace{11mu}{mg}}}$KEC is the potassium exchange capacity in mEq/g. The initialconcentration of potassium (ppm) is IC. The final concentration ofpotassium (ppm) is FC. The equivalent weight (atomic weight/valence) isEq wt. The volume (L) of standard in sample preparation is V. The weightof ZS-9 (mg) used for sample preparation is Wt_(spl). The percent (%) ofwater content (LOD) is % water.

Three samples of ZS-9 produced in accordance with the procedures ofExample 12, i.e., in a reactor without baffles (e.g., internal coolingcoil structure), were tested for potassium exchange capacity (KEC) inaccordance with the above-referenced procedure. Likewise, three samplesof ZS-9 produced in accordance with Example 14 in a reactor havingcooling coils serving as baffles were tested in accordance with thisprocedure. The results in Table 3 below show that the procedure ofExample 14 and the presence of baffles within the crystallization vesselresulted in a dramatic increase in the potassium exchange capacity.

TABLE 3 Potassium Exchange Capacity (KEC) Example 12 (Without baffles)Example 14 (With baffles) Lot 5368-10311A 2.3 meq/gm Lot 2724-9A 3.9meq/gm Lot 5368-12211A 1.7 meq/gm Lot 2724-13D 3.8 meq/gm Lot5368-13811A 1.8 meq/gm Lot 2724-18F 3.8 meq/gmThe high capacity ZS prepared in accordance with Example 14 will, uponprotonation using the techniques of Example 13, have a slightly lowerpotassium exchange capacity. The protonated ZS prepared in this way hasbeen found to have a potassium exchange capacity of about 3.2 meq/g.Accordingly, the high capacity ZS has been found to increase thecapacity of the protonated form prepared using this process. Thisdemonstrates that protonated ZS can be prepared having a potassiumexchange capacity within the range of 2.8 to 3.5 meq/g, more preferablywithin the range of 3.05 and 3.35 meq/g, and most preferably about 3.2meq/g.

EXAMPLE 16

The use of an internal cooling coil to provide a baffle-like structurewithin the reactor is only feasible for small reactors on the order of5-gallons because larger reactors cannot be easily fitted with, andtypically do not utilized, cooling coils.

The inventors have designed a reactor for larger-scale production ofhigh purity, high-KEC ZS-9 crystals. Large-scale reactors typicallyutilize a jacket for achieving heat transfer to the reaction chamberrather than coils suspended within the reaction chamber. A conventional200-L reactor 100 is shown in FIG. 17. The reactor 100 has smooth wallsand an agitator 101 extending into the center of the reaction chamber.The reactor 100 also has a thermowell 102 and a bottom outlet valve 103.The inventors have designed an improved reactor 200, FIG. 18, which alsohas an agitator 201, thermowell 202, and bottom outlet valve 203. Theimproved reactor 200 has baffle structures 204 on its sidewalls, whichin combination with the agitator 201 provide significant lift andsuspension of the crystals during reaction and the creation of highpurity, high KEC ZS-9 crystals. The improved reactor can also include acooling or heating jacket for controlling the reaction temperatureduring crystallization in addition to the baffle structures 204. Thedetails of an exemplary and non-limiting baffle design is shown in FIG.19. Preferably the reactor has a volume of at least 20-L, morepreferably 200-L or more, or within the range of 200-L to 30,000-L. Inan alternative embodiment, the baffle design may be configured to extendthe

EXAMPLE 17

The several dosages of ZS-9 were studied in the treatment of humansubjects suffering from hyperkalemia. A total of 90 subjects wereenrolled in the study. The study involved three stages with doseescalation of the ZS in each stage. The ZS-9 used in these studies wasprepared in accordance with Example 12. The ZS-9 crystals of anappropriate size distribution were obtained by air fractionation to havea distribution of crystals where greater than or equal to 97% are largerthan 3 microns. The screening is such that the ZS crystals exhibit amedian particle size of greater than 3 microns and less than 7% of theparticles in the composition have a diameter less than 3 microns. TheZS-9 crystals were determined to have a KEC of approximately 2.3 meq/g.The protonation is such that the ZS crystals exhibit a sodium contentbelow 12% by weight. The study utilized 3 g silicified microcrystalinecellulose, which are indistinguishable from ZS as the placebo.

Each patient in the study received either a 3 g dose of either theplacebo or ZS three times daily with meals. Both ZS and Placebo wereadministered as a powder in water suspension that was consumed duringmeals. Each stage of the study had a 2:1 ratio between the number ofsubjects in the ZS cohort and placebo. In stage I, 18 patients wererandomized to receive three daily doses of 0.3 g ZS or placebo withmeals. In Stage II, 36 patients were randomized to receive three dailydoses of 3 g ZS or placebo with meals. In Stage III, 36 patients wererandomized to receive three daily doses of 10 g ZS placebo with meals.Altogether there were 30 patients that received placebo and 60 patientsthat received various doses of ZS. Diet was essentially unrestricted,and patients were allowed to choose which food items they wished from avariety of local restaurants or the standard in-house diet of theclinic.

The screening value for potassium (“K”) was established on day 0 bymeasuring serum K three times at 30-minute intervals and calculating themean (time 0, 30 and 60 minutes). The baseline K level was calculated asthe mean of these values and the serum K on day one just beforeingestion of the first dose. If the screening K value was less than 5.0meq/1 the subject was not included in the study.

On study Days 1-2, all subjects received the study drug 3 times daily inconjunction with meals starting at breakfast (there was a delay of thefirst meal until 1.5 hours after the first dose on Day 1). Serum Klevels were evaluated 4 hours after each dose for 48 hours following theinitiation of treatment. If K levels became normal, the subject wasdischarged from the clinic at 48 hours without further study drugtreatment. If K levels were still elevated (K>5.0 meq/1), subjectsreceived another 24 hours of study drug treatment and then werere-assessed and discharged at 72 hours or 96 hours. All subjectsreceived a minimum of 48 hours of study drug treatment, but a fewreceived up to 96 hours of study drug treatment. The primary efficacyendpoint of the study was the difference in the rate of change inpotassium levels during the initial 48 hours of study drug treatmentbetween the placebo treated subjects and the ZS treated subjects. Table4 provides the p-values of the various cohorts at the 24 and 48 hourendpoints. Patients receiving 300 mg of the ZS three times daily had nostatistical difference relative to placebo at either of the 24 and 48hour endpoints. Patients receiving 3 grams of ZS demonstrated astatistical difference at only the 48 hour time period, suggesting thatthis particular dosing was relatively effective at lowering serumpotassium levels. Unexpectedly, those patients receiving 10 grams of ZSthree times daily demonstrated the greatest reduction in potassiumlevels in both concentration and in rate. The decrease in potassium wasconsiderable in magnitude, with an approximate 0.5 meq/g reduction atthe 3 gram dose and approximately 0.5-1 meq/g reduction at the 10 gramdosing.

TABLE 4 Primary endpoint: Serum potassium (mmol/l) exponential rate ofchange from 24 hours and 48 hours Intent-to-Treat Population (Primaryendpoint at 48 hours) Cohort 1 Cohort 2 Cohort 3 300 mg tid 3 g tid 10 gtid p-value p-value p-value 24 hours 0.7668 0.0737 0.1301 48 hours0.4203 0.0480 <0.0001

Subjects were then followed for a total of 7 days (168 hours) with Kmeasurements performed daily. 24 hour urine collections were performedon the day before the study (day 0) in all patients, and for as long asthe patients ingested the test product. Table 5 provides the differencein the rate of change in serum potassium levels over 7 days of studybetween placebo treated subjects and the various cohorts. Patientsreceiving 300 mg of the drug had no statistically significant reductionin potassium levels relative to the placebo over the 7 day period.Patients receiving 3 grams of the drug had no statistically significantreductions in potassium levels after the initial 24 hour period.Patients receiving 3 grams of the drug had the most statisticallysignificant reduction in serum potassium levels over the 7 day timecourse. These data suggests that when given at least 10 grams of ZS, anextended reduction of potassium is achieved, and that a single (i.e., 1day) dose is suitable for significant reduction in potassium levels. Itis also possible that dosages of 3,4, or 5 grams may be effective atreducing the potassium levels when given once daily.

TABLE 5 Serum Potassium (mmol/l) over time in intent-to-treat populationCohort 1 Cohort 2 Cohort 3 300 mg tid 3 gm tid 10 gm tid Unpaired t-testUnpaired t-test Unpaired t-test p-value p-value p-value Baseline Day1-30 Min 0.566 0.604 0.356 Post 1^(st) Day 1-1 Hr 0.875 0.125 0.022 Post1^(st) Day 1-2 Hr 0.231 0.688 0.160 Post 1^(st) (Fed Breakfast) Day 1-4Hr 0.640 0.774 0.232 Post 1^(st) (Fed Lunch) Day 1-4 Hr 0.219 0.4150.072 Post 2^(nd) Day 1-4 Hr 0.603 0.365 0.025 Post 3^(rd) Day 2-0 Hr0.700 0.026 0.092 Day 2-4 Hr 0.675 0.136 <0.001 Post 1^(st) Day 2-4 Hr0.891 0.044 <0.001 Post 2^(nd) Day 2-4 Hr 0.783 0.064 <0.001 Post 3^(rd)Day 2-20 Hr 0.822 0.157 <0.001 Post 1^(st) Day 3-0 Hr 0.914 0.074 <0.001Day 4-0 Hr 0.756 0.775 <0.001 Day 5-0 Hr 0.404 0.595 0.001 Day 6-0 Hr0.717 0.321 0.016 Day 7-0 Hr 0.217 0.476 0.065

Comparison of treatment groups demonstrated no significant difference inany parameters including: age, sex, weight, serum creatinine level,estimated Glomerular filtration rate (“GFR”), potassium levels, andcause of Chronic Kidney Disease (“CKD”).

FIG. 20 shows changes in serum K in the first 48 hours after ingestionof the placebo, ZS at 0.3 g per dose (Cohort 1), ZS at 3 g per dose(Cohort 2) and ZS at 10 g per dose (Cohort 3). Slopes of K versus timefor the patients administered ZS were significantly different from theplacebo for Cohort 2 (0.5 meq/L/48 hours, P<0.05) and Cohort 3 (1meq/L/48 hours P<0.0001).

The time to normalization of serum K was significantly less in Cohort 3versus the placebo group (P=0.040). Results for the other Cohort groupswere not significantly different from placebo. FIG. 21 compares the timeto decrease of serum K by 0.5 meq/L for subjects administered ZS at the10 g doses versus placebo. Time to decrease in serum K was significantlyshorter in ZS administered subjects than in placebo (P=0.042).

The increase in serum K from 48 hours to 144 hours of the study was alsoexamined after discontinuing the administration of the study drug. Therate of increase in serum K was roughly proportional to the rate ofdecrease in serum K during ingestion of the drug, as shown in FIG. 22.

Analysis of 24 hour urine K excretion demonstrated that there was asignificant (P<0.002) decrease of approximately 20 meq/day in urinary Kexcretion for ZS at the 10 g dose, while excretion remained the same orincreased in all other groups as shown in FIG. 23.

Analysis of the K/creatinine ratio in daily urine samples confirmed thesame trends as in 24 hour urine K excretion. Cohort 3 had a downwardtrend in urinary K/creatinine ratio while the other Cohorts remainedconstant or increased. Separate analysis indicated no change increatinine clearance or daily creatinine excretion in any of the groupsduring the study.

Analysis of the 24 hour urine samples also allowed calculation of theurinary daily sodium excretion. As shown in FIG. 24, sodium excretionwas generally stable in all of the groups. Urinary sodium excretionappeared to rise more in Cohort 1 and Control patients than in Cohort 3though there were no significant changes in any group.

Blood Urea Nitrogen (“BUN”) was tested as a measure of the effect of ZSto bind ammonium which is generated by bacterial urease in the gut.There was a dose-related and statistically significant reduction in BUNfrom Study Day 2 to Study Day 7, mirroring that of serum K (p-valuesbetween 0.035 [Study Day 2] and <0.001 [Study Days 5-7]). This was alsoaccompanied by a reduction in urine excretion of urea.

There was a statistically significant decrease in serum calcium thatremained within the normal range (from 9.5 mg/dL to 9.05 mg/dL) at the10 g three times daily dose of ZS (p-values from 0.047 to 0.001 on StudyDays 2-6, but no subjects developed hypocalcemia; there were nosignificant changes in serum magnesium, serum sodium, serum bicarbonateor any other electrolytes at any dose level of ZS. There was a trendtowards a reduction in serum creatinine, which became statisticallysignificant on Study Day 6 (p=0.048). There were no dose-related changesin any other evaluated kidney parameters, including urinary sediment,estimated Glomerular filtration rate (“GFR”) or the renal biomarkersNGAL and KIM-1.

This clinical trial, which was randomized and double-blind, demonstratesthat ingestion of moderate amounts of ZS significantly decreases serum Klevels in patients with Stage 3 CKD. No laxative agents were given withthe ZS, so the removal of K was solely due to the binding of K in thegut by ZS, rather than due to effects of diarrhea.

Oral sodium polystyrene sulfonate (“SPS”) therapy invariably causessodium load to the patient. Sodium is released in 1:1 ratio of thebinding of all cations (K, hydrogen, calcium, magnesium, etc.). ZS isloaded partly with sodium and partly with hydrogen, to produce a nearphysiologic pH (7 to 8). At this starting pH, there is little release ofsodium and a some absorption of hydrogen during binding of K. Urinaryexcretion of sodium does not increase during ingestion of ZS and thus ZSuse should not contribute to sodium excess in patients.

The rapidity of action of ZS on serum K and the effectiveness indiminishing K excretion in the urine is surprising at the maximum doseof about 10 g three times daily (about 30 g daily or about 0.4g/kg/day). This also resulted in a fall in urinary K by the second dayof about 40% from the baseline level. It thus appears that ZS is atleast as effective in diminishing body K stores in humans as in animals,and possibly more so due to the high K concentration in human stool.

EXAMPLE 18

High capacity ZS (ZS-9) is prepared in accordance with Example 14. Thematerial is protonated in accordance with the techniques described inExample 13. The material has been screened such that the ZS crystalsexhibit a median particle size of greater than 3 microns and less than7% of the particles in the composition have a diameter less than 3microns. The ZS crystals exhibit a sodium content below 12% by weight.The dosage form is prepared for administration to patients at a level of5 g, 10 g, and 15 g per meal. The ZS in this example has an increasedpotassium exchange capacity of greater than 2.8. In a preferred aspect,the potassium exchange capacity is within the range of 2.8 to 3.5 meq/g,more preferably within the range of 3.05 and 3.35 meq/g, and mostpreferably about 3.2 meq/g. A potassium exchange capacity target ofabout 3.2 meq/g includes minor fluctuations in measured potassiumexchange capacity that are expected between different batches of ZScrystals.

The ZS-9, when administered according to the protocol established inExample 17, will provide for a similar reduction in potassium serumlevels. Because ZS-9 has an improved KEC, the dosing administered to thesubject in need thereof will be lowered to account for the increasedcation exchange capacity. Thus, to patients suffering from potassiumlevels elevated above the normal range, approximately 1.25, 2.5, 5, and10 grams of the ZS-9 will be administered three times daily.

Other embodiments and uses of the invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein. All references cited herein,including all U.S. and foreign patents and patent applications, arespecifically and entirely hereby incorporated herein by reference. It isintended that the specification and examples be considered exemplaryonly, with the true scope and spirit of the invention indicated by thefollowing claims.

EXAMPLE 19

ZS (ZS-2) is prepared in accordance with known techniques of U.S. PatentNos. 6,814,871, 5,891,417, and 5,888,472, discussed above. The x-raydiffraction pattern for the ZS-2 has the following characteristicsd-spacing ranges and intensities:

TABLE 6 ZS-2 d (Å) I 5.8-6.6 m 4.2-5.0 w 3.9-4.6 m 2.9-3.7 m 2.5-3.3 vs2.3-3.0 sIn one aspect of this example, the ZS-2 crystals are prepared using thereactor with baffles described in Example 14. The material is protonatedin accordance with the techniques described in Example 13. The materialhas been screened such that the ZS crystals exhibit a median particlesize of greater than 3 microns and less than 7% of the particles in thecomposition have a diameter less than 3 microns. The ZS crystals exhibita sodium content below 12% by weight. The dosage form is prepared foradministration to patients at a level of 5 g, 10 g, and 15 g per meal.The ZS-2 crystals prepared in accordance with this example arebeneficial for reducing serum potassium and can be manufactured usingthe alternative techniques for making ZS-2. These alternativemanufacturing techniques may provide advantages under certaincircumstances.

EXAMPLE 20

Several batches of protonated ZS crystals were prepared using thereactor described in Example 16.

The batches of the ZS crystals were generally prepared in accordancewith the following representative example.

The reactants were prepared as follows. To a 200-L reactor, as shown inFIG. 17, sodium silicate (56.15 kg) was added and charged with deionizedwater (101.18 kg). Sodium hydroxide (7.36 kg) was added to the reactorand allowed to dissolve in the reactor in the presence of rapid stirringover a period of greater than 10 minutes until there was completedissolution of the sodium hydroxide. Zirconium acetate (23 kg) was addedto the reactor in the presence of continuous stirring and allowed tostir over a period of 30 minutes. The reactants were mixed at a rate 150rpm with the reactor set to 210° C.±5° C. for a period of ≧60 hours.

After the reaction period, the reactor was cooled to 60° C.-80° C. andthe slurry of reactants were filtered, washed and dried over a period of≧4 hours at a temperature of approximately 100° C. To prepare the driedcrystals for protonation, deionized water (46 L) was charged tore-slurry the crystals. A solution of 15% HCl (approximately 5 to 7 kgof the 15% HCl solution) was mixed with the slurry for a period of 25 to35 minutes. Following the protonation reaction, the reactants were onceagain filter dried and washed with approximately ≧75 L of deionizedwater.

Exemplary details of several protonated ZS crystal batches producedutilizing the above described procedure are presented in Table 7:

TABLE 7 Lot Number 5602- 5602- 5602- 5602- 26812-A 28312-A 29112-A29812-A Yield (kg) 16.60 16.65 16.61 16.14 % 95 94.5 94.7 92.2Theoretical Yield IP KEC 3.35 2.9 2.46 2.92 XRD 28.9 28.9 28.9 28.9highest XRD 2nd 15.5 15.5 15.5 15.5 highest XRD 3rd 26.2:13.9 26.1:13.926.2:26.2 26.2:26.2 highest pH 8.3 8.7 8.6 8.9 % < 3 um 0.4 1.27 1.523.08 (2.50) % < 3 um 1.69 2.77 2.8 6.37 (3.00) Mean 10.6 12.5 12.8 10.1D(4.3) KEC 3.1 3.0 2.94 3.04

The XRD plot of the H-ZS-9 obtained above are provided in FIGS. 25-28.The XRD plots demonstrate that H-ZS-9 can be manufactured incommercially significant batch quantities having desired potassiumexchange capacity. Lot 5602-26812-A attained the most uniformcrystalline distribution. It was found that when crystallizationconditions result in a highly uniform particle size distribution, thesubsequent protonation step reduced the cation exchange capacity from3.4 to 3.1 meq/g. In contrast, Lots 5602-28312-A, 5602-29112-A, and5602-29812-A exhibited a less uniform particle size distribution. Theless uniform particle size distribution resulted from increasing thefill ratio of the reactor. When fill ratios reached 80-90%, the particlesize distributions became less uniform. Unexpectedly, however, thesubsequent protonation of these lots resulted in a significant increasein the potassium exchange capacity. Because the reaction according tothe invention can be run in a manner that increases potassium exchangecapacity upon protonation, it is expected that higher capacity ZS-9 canbe obtained in commercially significant quantities than otherwise wouldhave been thought possible.

Phase quantification to determine the diffraction pattern of the variousbatches of protonated ZS crystal samples were also performed using theRietveld method in a Rigaku MiniFlex600. Manufacturing procedures usingthe 200-L reactor produced the phase composition described in Table 8and XRD data described in FIGS. 25-29.

TABLE 8 Phase Composition (wt %) via Reitveld Analysis Lot Number ZS-9ZS-7 ZS-8 Amorphous Crystals 5567-26812-A 61.6 16.0 22.3 5567-28312-A55.7 21.8 22.5 5567-29112-A 55.7 25.7 18.6 5567-29812-A 66.6 19.1 14.3

The diffraction patterns for the batches produced provided a mixture ofZS-9 and ZS-7 crystals in additional to a series of amorphous crystals.It was found that ZS crystals made in the larger 200 L reactor accordingto the above processes resulted in no detectable levels of ZS-8 crystalsand lower levels of amorphous material than previously produced. Theabsence of ZS-8 crystals is highly desirable due to the undesirablyhigher solubility of ZS-8 crystals and their attendant contribution toelevated levels of zirconium in urine. Specifically, levels of zirconiumin the urine are typically around 1 ppb. Administration of zirconiumsilicate containing ZS-8 impurities has led to zirconium levels in theurine between 5 to 50 ppb. The presence of ZS-8 can be confirmed by XRDas shown in FIG. 30. The ZS-9 crystals according to this embodiment areexpected to lower levels of zirconium in the urine by eliminatingimpurities of soluble ZS-8 and minimizing the amorphous content.

EXAMPLE 21

The batches of protonated zirconium crystals described in Example 20were used in studies to treat human subjects suffering fromhyperkalemia. The ZS compositions were generally characterized as havinga mixture of ZS-9 and ZS-7, where the ZS-9 was present at approximately70% and the ZS-7 was present at approximately 28% (hereafter ZS-9/ZS-7).All of the characterized ZS-9/ZS-7 crystals lack detectable quantitiesof ZS-8 crystals. Subjects were administered the ZS-9/ZS-7 compositionaccording the method described in Example 17. A summary of the resultsare provided in Table 9.

TABLE 9 Kidney Function Test using the ZS-9/ZS-7 composition Subject IDLab Test Day 0 Day 3 Day 4 Day 5 Day 6 Day 9 Day 15 Day 21 009-006 L-DBUN 64.6 71.3 77.2 80.7 82.5 78.1 64.4 63.7 Creat 2.37 2.38 NA NA NA2.37 2.34 2.40 009-011 BUN 28.5 27.9 31.7 28.1 28.1 22.2 32.6 36.9 CHRCreat 2.31 2.27 NA NA NA 2.21 2.32 2.54 009-014 BUN 18.6 15.6 16.1 15.614.4 15.6 18.5 18.9 RWR Creat 1.11 1.13 NA NA NA 1.23 1.13 1.16 009-017BUN 60.3 61.7 67.1 75.3 75.2 75.9 71.3 74.4 SMK Creat 2.37 2.31 NA NA NA2.31 2.29 2.61 009-019 BUN 51.4 41.9 44.8 ND 41.4 37.7 46.6 GLS Creat3.14 2.71 NA ND NA 2.33 2.85 009-022 BUN 87.3 103.3 101.6 ND 94.6 85.376.4 97.8 JHR Creat 2.40 2.40 NA ND NA 2.50 1.93 3.00 009-023 BUN 42.339.5 36.3 39.9 36.5 37.9 37.4 33.5 EEF Creat 2.50 2.48 NA NA NA 2.222.44 2.39 009-025 BUN 42.4 43.1 37.9 ND 28.2 25.9 31.3 DHK Creat 2.352.09 NA ND NA 1.82 2.05 009-026 BUN 24.3 25.5 28.5 ND 27.1 29.1 35.4 ABLCreat 2.02 2.04 NA ND NA 1.99 1.94 009-028 BUN 46.9 55 GMS Creat 4.514.61 NA NA NA

Surprisingly, the glomerular filtration rate (GFR) for subjectsadministered the ZS-9/ZS-7 composition were unexpectedly higher relativeto the patient's baseline. Without being bound to any particular theory,the inventors posit that the improved GFRs and lowered creatinine levels(see Table 9 above) are due to absence of the ZS-8 impurities in theZS-9/ZS-7 composition. As is generally known in the prior art, ZS-8crystals have been characterized as having a higher solubility andtherefore is able to circulate systemically. This, the inventorsbelieve, may be the causes of elevated BUN and creatinine levels uponadministration of zirconium crystals described in the prior art.

This clinical trial demonstrates that ingestion of moderate amounts ofZS-9/ZS-7 surprisingly and unexpectedly decreases creatinine levels inpatients.

Other embodiments and uses of the invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein. All references cited herein,including all U.S. and foreign patents and patent applications, arespecifically and entirely hereby incorporated herein by reference. It isintended that the specification and examples be considered exemplaryonly, with the true scope and spirit of the invention indicated by thefollowing claims.

The invention claimed is:
 1. A zirconium silicate composition comprisingzirconium silicate of formula (I):A_(p)M_(x)Zr_(1-x)Si_(n)Ge_(y)O_(m)  (I) where A is a potassium ion,sodium ion, rubidium ion, cesium ion, calcium ion, magnesium ion,hydronium ion or mixtures thereof, M is at least one framework metal,wherein the framework metal is hafnium (4+), tin (4+), niobium (5+),titanium (4+), cerium (4+), germanium (4+), praseodymium (4+), terbium(4+) or mixtures thereof, “p” has a value from about 1 to about 20, “x”has a value from 0 to less than 1, “n” has a value from 1 to about 12,“y” has a value from 0 to about 12, “m” has a value from about 3 toabout 36 and 1≦n+y≦12, wherein the composition comprises ZS-9 and ZS-7and lacks detectable amounts of ZS-8.
 2. The composition of claim 1,wherein the ZS-9 has an X-ray diffraction pattern of d (Å) 5.9-6.75.3-6.1 2.7-3.5 2.0-2.8 1.6-2.4.


3. The composition of claim 1, wherein the ZS-7 has an X-ray diffractionpattern of d (Å) 6.8-7.6 5.6-6.4 3.7-4.5 3.6-4.4 2.6-3.4 2.5-3.32.4-3.2.


4. The composition of claim 1, wherein the ZS-8 has an X-ray diffractionpattern of d (Å) 12.0-13.2 3.9-4.7 2.8-3.6 2.3-3.1 2.2-3.0 2.1-2.9.


5. The composition of claim 1, wherein the composition comprises ZS-9 ata weight percent ranging from about 50% to about 75%.
 6. The compositionof claim 1, wherein the composition comprises ZS-7 at a weight percentranging from about 25% to about 50%.
 7. The composition of claim 1,wherein the ZS-9 exhibits a median particle size of greater than 3microns and less than 7% of the particles in the composition have adiameter less than 3 microns, and the composition exhibits a sodiumcontent below 12% by weight.
 8. The composition of claim 1, wherein theZS-9 is partially protonated.
 9. The composition of claim 1, wherein theprotonated ZS-9 has a potassium exchange rate of greater than 3.1 meq/g.10. The composition of claim 1, wherein the protonated ZS-9 has apotassium exchange rate in the range of 3.2 to 3.5 meq/g.
 11. Thecomposition of claim 1, wherein the protonated ZS-9 has a potassiumexchange rate of >2.46 meq/g.
 12. The composition of claim 1, whereinthe protonated ZS-9 has a sodium content of less than 12%.
 13. Anzirconium silicate composition comprising zirconium silicate of formula(I):A_(p)M_(x)Zr_(1-x)Si_(n)Ge_(y)O_(m)  (I) where A is a potassium ion,sodium ion, rubidium ion, cesium ion, calcium ion, magnesium ion,hydronium ion or mixtures thereof, M is at least one framework metal,wherein the framework metal is hafnium (4+), tin (4+), niobium (5+),titanium (4+), cerium (4+), germanium (4+), praseodymium (4+), terbium(4+) or mixtures thereof, “p” has a value from about 1 to about 20, “x”has a value from 0 to less than 1, “n” has a value from 1 to about 12,“y” has a value from 0 to about 12, “m” has a value from about 3 toabout 36 and 1≦n+y≦12, wherein the zirconium silicate comprises ZS-9 ata weight percent ranging from about 50% to about 75%, and ZS-7 at aweight percent ranging from about 25% to about 50%.
 14. The compositionof claim 13, wherein the ZS-9 has an X-ray diffraction pattern of d (Å)5.9-6.7 5.3-6.1 2.7-3.5 2.0-2.8 1.6-2.4.


15. The composition of claim 13, wherein the ZS-7 has an X-raydiffraction pattern of d (Å) 6.8-7.6 5.6-6.4 3.7-4.5 3.6-4.4 2.6-3.42.5-3.3 2.4-3.2.


16. The composition of claim 13, wherein the composition does notcomprise a ZS-8 having an X-ray diffraction pattern of d (Å) 12.0-13.23.9-4.7 2.8-3.6 2.3-3.1 2.2-3.0 2.1-2.9.


17. The composition of claim 13, wherein the composition comprises ZS-9at a weight percent ranging from about 50% to about 75%.
 18. Thecomposition of claim 13, wherein the composition comprises ZS-7 at aweight percent ranging from about 25% to about 50%.
 19. The compositionof claim 13, wherein the ZS-9 exhibits a median particle size of greaterthan 3 microns and less than 7% of the particles in the composition havea diameter less than 3 microns, and the composition exhibits a sodiumcontent below 12% by weight.
 20. The composition of claim 13, whereinthe ZS-9 is partially protonated.
 21. The composition of claim 13,wherein the protonated ZS-9 has a potassium exchange rate of greaterthan 3.1 meq/g.
 22. The composition of claim 13, wherein the protonatedZS-9 has a potassium exchange rate in the range of 3.2 to 3.5 meq/g. 23.The composition of claim 13, wherein the protonated ZS-9 has a potassiumexchange rate of >2.46 meq/g.
 24. The composition of claim 13, whereinthe protonated ZS-9 has a sodium content of less than 12%.